Original subtitles

This show is fictitious.

There is not actually an asteroid

headed to New York City today,

but this is based on simulations of such an event.

We run simulations of fictional asteroid strike

to prepare for the worst-case scenario.

[Mike Rowe] November 4, 2029.

We face a countdown to catastrophe.

A giant asteroid hurtles towards Earth.

It's heading straight for

the eastern seaboard of the United States.

The space rock could wipe out an entire city

and cause widespread devastation.

Can Earth survive?

[electricity crackles]

[explosion]

New York City, November 4, 2029.

The deserted metropolis waited for the asteroid to strike.

A giant space rock entered the atmosphere,

heading straight for the eastern seaboard of the USA.

[Plesko] As it comes through the atmosphere,

we would see something as bright as the sun getting

brighter and brighter and brighter.

[Durda] At speeds of maybe 20 kilometers per second or so.

That's something like 18 times faster than

the speed of a bullet coming out of a rifle.

This asteroid was headed towards

the most populous city in America,

and when it impacts, it would deliver

more energy than 1,000 Hiroshima nuclear bombs.

[ explosion ]

It would level some of the most expensive real estate

in the world in seconds.

There would be a crater where Central Park used to be.

I actually don't even like thinking about this,

[ stammering ]

of how horrible it would be.

[Plait] This is beyond the worst disaster

the world has-- would have ever faced.

There's nothing in our history that would have

done this much damage so quickly and so devastatingly.

[Rowe] The story of the asteroid

and the Earth's fight back

started seven years ago, here in Arizona.

September 2022,

the Catalina Sky Survey.

Guardian of heavens Greg Leonard drives

to Mount Lemmon Observatory near Tucson.

He's on the hunt for asteroids and comets.

[Leonard] We are the watchers of the skies for the planet.

We literally represent the first line of defense

against potentially incoming asteroids,

and I want to emphasize the words planetary defense.

This is not in the benefit for one nation.

This is for the entire planet.

[Rowe] Greg takes a series of images

over a 20-minute period.

Stars don't move in the photos,

but asteroids and comets do.

A-ha.

We can see four points of light

tracking across the background of the stationary stars.

This one is moving very quickly across the sky.

So this tells me

this is a real near-Earth asteroid candidate.

[Rowe] It's one of over 27,000 near-Earth asteroids,

or NEAs for short, discovered by the early 2020s.

The huge gravity of Jupiter can rip space rocks

from their home in the asteroid belt.

Some race outwards, away from the sun.

NEAs head inwards, occasionally towards Earth.

We didn't know it back in September of 2022,

but these were our first images

of a deadly incoming asteroid.

[Leonard] It's relatively close to Earth's neighborhood.

We don't know exactly how far it is yet,

but it's close enough where its motion across the sky

appears rapid.

[Rowe] The discovery of an NEA set a series

of planet protection protocols in motion.

Step one, enlist a global team of experts

to investigate the asteroid's orbit.

[Plesko] We have some of the brightest minds,

some of the best telescopes,

some of the biggest supercomputers

working to protect Earth,

collaborating across language barriers,

across international borders to protect humanity.

[Rowe] This international planetary defense team

was tasked with discovering if the distant object

would become a serious threat to Earth.

Their first job--

determine if the NEA's orbit would intersect with our own.

[Plait] Orbits are a little like roads, right?

You've got a path that something follows,

and they can intersect, you can have a crossroads.

Now, typically, if only one object is there,

that's not a big deal,

but if you have two objects approaching that intersection

at the same time, they could collide,

and that's the danger from asteroids.

[Rowe] The team of scientists

track the asteroid for four months.

[Chodas] Over time, you can build up observations.

You can gradually narrow down the possible number of orbits,

then determine whether there's any chance of a future impact,

but if the asteroid is orbiting the sun,

the Earth is orbiting the sun, and there's this dance going on.

Sometimes the asteroid is near the Earth,

and we can observe it, it's bright.

Other times the asteroid is

on the other side of the sun.

We can't observe it at all.

[Rowe] We were lucky.

The asteroid was visible throughout the fall of 2022.

However, our observations of the space rock's orbit

showed a very real possibility

that it would slam into Earth in just seven years.

[ whooshing ]

Astronomers gave the incoming asteroid

a suitably appropriate name, Apep.

Apep was the Egyptian god of chaos,

so that's a fairly good name for an asteroid

that could hit the Earth

because that's exactly what would happen.

You'd have chaos, destruction, and death.

[Rowe] A catalog of devastation to be unleashed on Earth.

But just how bad would the impact be?

[Rowe] January 2023.

Asteroid Apep was on a collision course with Earth.

Step two in our planetary defense--

know your enemy and build up a picture of the asteroid.

Apep was 1,800 feet wide,

five times the length of a football field.

Its huge size bumps it up into a new category of asteroids.

Apep was what we refer to as

a PHA, a potentially hazardous asteroid.

We're talking about something

that is a third of a mile across.

This is enormous.

An 1,800-foot-wide asteroid is about 112 million metric tons.

[Rowe] That's over 300 times the weight of the Empire State Building.

Computer simulations of the impact

of an asteroid that massive hitting a city

revealed extraordinary levels of destruction.

An 1,800-foot-diameter asteroid,

that would create a crater

that's 3 or 4 miles across, 1,600 feet deep.

It would have a radiation blast wave that

would set things on fire for about 20 miles,

but no sooner would things be lit on fire,

there would be a 500-mile-an-hour wind

radiating out,

leveling buildings, knocking down trees,

destroying highways.

100 miles away, you'd still feel a magnitude seven earthquake.

It's not easy to say what is going to kill you first.

It's probably going to be simply the flash of energy.

There's so much heat from this thing that you can be vaporized.

If you somehow survived that,

then there's going to be the blast wave that will

pulverize anything in its path.

[Rowe] To build an accurate simulation,

the scientists used more than size and mass.

They also studied its composition

and the speed of its orbit.

[Fast] You need to know what an asteroid is made of,

the speed of that asteroid,

how large it is in order to understand,

will it make it through Earth's atmosphere,

and what might the impact effects be?

[Rowe] Asteroids vary in composition and structure.

Some are loose collections of small rocks,

others rocky and compact.

The most dangerous are metallic.

A metal asteroid can be five times as dense

as some of the lower density asteroids,

and so for the same speeds on the same orbits

they pack way more punch when it comes to an impact.

[Thaller] If you want to see exactly

what a metallic asteroid can do,

go no farther than Barringer Crater in Arizona.

Now that crater is about a mile across,

and the meteor that made it was only about 150 feet across.

[Rowe] Arizona, 50,000 years ago.

The last major asteroid strike on present day North America,

a tiny metallic space rock

hits the ground at 25,000 miles an hour,

releasing energy equivalent to 2.5 million tons of TNT.

Scale that up to the size of 1,800-foot Apep,

and it would create a blast wave the size of Delaware.

If Apep were a metal asteroid, it would tear through

the atmosphere like a cosmic bullet.

In a modern city, without warning,

it could kill a lot of people.

But although they're very dangerous,

they're also very rare.

[Rowe] More common are rubble piles,

loose collections of small rocks held together by gravity.

Rubble pile is kind of the perfect name for them,

but you can think of them as like a literally

a pile of stuff out of a dump truck in your driveway,

but if you take that and you put that in space,

they don't have much gravity but they have enough to stay

bound to each other,

and that's your rubble pile asteroid.

They are just barely holding on to themselves.

If you were to come and just apply sufficient gravity,

you could rip it apart.

[Rowe] Pressure and heat from entering our atmosphere

can also tear a rubble pile asteroid to pieces,

but that can be just as dangerous to a city below.

The breakup of an asteroid in

the upper atmosphere is-- is pretty devastating.

It's like a nuclear weapon going off in the atmosphere,

flattening buildings and breaking windows.

There are going to be mass casualties

from an event like that

due to just the injuries from flying glass and debris.

[Rowe] To discover what type of asteroid Apep belonged to,

the planetary protection team

train their telescopes onto the space rock.

Analysis revealed that Apep was a rocky,

carbonaceous chondrite asteroid, or C-type for short.

C-type asteroids like Apep

are less dense than metal asteroids,

but more solid than rubble piles.

If a big enough C-type asteroid

penetrates the Earth's atmosphere,

it has the chance to make it all the way down to the surface.

It doesn't necessarily burn up in the atmosphere.

[Rowe] Apep's size, mass, and composition told us

it would punch through our atmosphere and hit the surface.

The final piece of information needed to accurately predict

the true amount of damage from the impact

was Apep's kinetic energy, the amount of energy

the asteroid would punch into the ground.

The kinetic energy of an object depends on the mass,

and it depends even more strongly on the speed.

More mass creates more kinetic energy,

but more velocity will increase the kinetic energy by

a squared factor.

For example, if something has twice the velocity,

it will have four times the same energy.

[Rowe] Scientists calculated how much energy Apep,

weighing in at 123 million tons

and traveling at 40,000 miles an hour,

would transfer into the Earth.

So what kind of energies were involved here?

Uh, you know, 1,800-foot diameter asteroid.

It's 112 million tons,

and it's traveling at 40,000 miles per hour.

That's something on the order of

10 to the 19th joules of energy,

a one followed by 19 zeros.

1.8 times 10 to the 19 joules is equivalent to 5,000 megatons.

Take a one megaton nuke,

a substantial nuclear weapon, and then blow up 5,000 of them.

That is roughly the same amount as all the nuclear

weapons on Earth,

detonating all at once.

[Rowe] A strike this large would affect the whole planet.

[Sutter] This would have global impacts.

We would have to deal with the fallout,

the literal fallout from this event for--

for potentially 1,000 years.

[Rowe] Spring, 2023.

We had two choices--

do nothing and face a planet-changing catastrophe,

or fight back.

We chose to take on Apep.

It was the first time in human history

that we might actually be able to prevent a natural disaster

from happening.

We could plan and launch a response mission,

so we don't have to get out of the way.

Make it get out of the way instead.

[Rowe] The mission's objective was simple--

stop the asteroid, and save the world.

We can't superglue an earthquake fault shut.

We can't cork volcanoes,

but planning for an asteroid impact

is something we really could do.

[Rowe] June 2023.

A large asteroid was headed towards Earth.

It was predicted to strike on November 4, 2029.

To protect our planet,

A team of scientists plan to deflect the asteroid.

[Sutter] An 1,800-foot wide asteroid

was headed towards the Earth.

We needed it to go in literally any other direction.

[Rowe] So how could we push Apep off course?

Scientists found a clue in the asteroid belt.

Sometimes the lumps of space debris collide

and change their trajectory.

Maybe we could replicate this and deflect Apep.

We could try to deflect the asteroid and change its orbit

so that it actually misses the Earth.

[Sutter] If you do it early enough,

it may not be much, less than half a millimeter per second,

but that is enough.

These asteroids travel for millions of miles, and so over

the course of days, weeks,

months, and years, it will have a radically different orbit.

[Rowe] Sounds simple.

Send up a rocket with a robotic space probe,

travel millions of miles, and knock Apep away from Earth.

Piece of cake.

In the movies,

when there's a threatening asteroid that's found,

there's always a rocket on the pad ready to go after that,

and it's not the case in real life.

It takes years to design the mission,

to build the satellite, to launch it,

and then it has to get there,

and that might be millions of miles away from Earth.

[Rowe] Fortunately, Earth had a head start.

We detected Apep early,

and we'd already built an asteroid deflector called

the Double Asteroid Redirection Test,

or DART for short.

In 2021 we sent DART 6.8 million miles

to rendezvous with an asteroid called Didymos.

Didymos posed no threat to Earth,

but allowed us to test the technology.

[Thaller] The asteroid called Didymos

has a small moon asteroid going around it.

The point of the DART mission

was to send an impactor into this little moon

and see how much we nudge it off the orbit that it's in.

[Rowe] Lessons learned from DART

would inspire a new mission.

November 2025.

We launched the DAAFE mission--

deflect Apep away from Earth.

This wasn't a test run to a safe asteroid.

This was the real deal, a mission to save our planet.

It was an enormous technical challenge,

and we had no idea if it would work.

When you think about a spacecraft going from Earth

millions of miles away to hit an asteroid

at an exact point in time,

at an exact point in space.

It's really the ultimate bullseye.

It's like trying to hit one bullet with another bullet

launched from the other side of a continent.

[Rowe] November 2028.

After three years in space, DAAFE arrived at Apep.

This was our last chance.

This was our only chance.

[Rowe] The kinetic impactor

smashed into Apep at 14,000 miles an hour.

On Earth, telescopes and radar tracked the collision.

Did it work?

Did we push the asteroid off course?

At first glance, the mission worked.

We deflected Apep away from us.

[Rowe] It looked like the mission worked.

[Plait] As an astronomer, and, you know,

a human who has to live on this planet,

I was very happy, right?

We've just literally saved the world.

[Rowe] But the happiness was short-lived.

There was a problem.

The collision had pushed Apep away from Earth,

but it also sheared off a 300-foot chunk of rock.

This smaller asteroid, called Apep 2.0,

could still be a significant threat.

A 300-foot chunk of rock is still very, very large.

300 feet wide.

That's almost a football field.

[Plesko] So the important things we needed to know--

was it going to hit us?

And if so, where is it going to hit us?

[Rowe] March 2029, we got our answer.

Its point of impact--

The east coast of the United States,

with New York City in the firing line.

SUTTER: A smaller chunk headed for New York City.

This was the worst-case scenario.

I want to emphasize,

there's no asteroid headed toward New York tonight.

This is just a discussion about

what this process would be like.

[Rowe] In 2028,

we tried to deflect Apep away from Earth.

The mission wasn't a complete success.

Yes, we managed to actually divert

the large asteroid away from hitting the Earth,

but in doing so, we broke off a clump big enough

to be very dangerous heading toward the eastern seaboard.

[Rowe] June 2029, five months to impact.

The future looked bleak for New York,

but it wasn't the time to give up.

They reassessed an idea

first suggested to destroy the original 1,800-foot Apep,

a nuclear strike.

It worked in Armageddon.

Maybe it would work in real life.

However, studies revealed that nuking an asteroid

wasn't as simple as it looks in a Hollywood movie.

Hey, let's blow it up.

Let's nuke it, right?

Well, instead of one big problem,

now you have slightly smaller problems,

and they're radioactive, by the way.

So you don't want to do that.

[Rowe] Computer simulations revealed

that even the world's largest

nuclear weapon had only 1 percent of the energy needed

to destroy the original 1,800-foot Apep.

We needed the world's most powerful nuclear weapon

and 99 of its best friends, launch them all simultaneously,

and have them simultaneously hit the asteroid.

It was simply beyond our technological capabilities.

[Rowe] Fortunately, thanks to the DAAFE mission,

we only had to take out the 300-foot Apep 2.0.

Could we blow the smaller asteroid out of the sky?

Maybe, but launching a nuclear Hail Mary

would be very controversial.

Nuclear devices are the most powerful,

really, one of the most emotional

things that humans have ever invented.

[Rivkin] They are the most powerful tool in our toolbox.

We've got a hammer, and it's a very big hammer,

but there are a lot of concerns with them,

so they cannot be tested in space,

according to international law.

[Rowe] Without being able to test nukes in space,

they were considered too big a risk,

but New York had one final potential savior,

the Earth itself.

2013, Chelyabinsk, Russia.

An asteroid blew up in the atmosphere.

It didn't make it all the way to the surface,

and the people in Chelyabinsk are very lucky because of that.

[Rowe] The 60-foot-wide Chelyabinsk asteroid

was rocky like Apep,

and it moved at a similar velocity,

around 40,000 miles an hour,

but it met its match when it entered Earth's atmosphere.

Earth's atmosphere doesn't look like much.

You think, oh, it's just air, it doesn't matter,

but all of those molecules actually exert pressure

on the front edge of the asteroid,

slowing it down and heating it up.

Rock heated up

and began to crumble and explode as it came through.

[Rowe] The midair explosion, called an airburst,

released more energy than 440,000 tons of TNT.

The shockwave traveled 100 miles,

damaging 7,000 buildings

and injuring 1,500 people.

But a ground strike hitting a city

would have been a lot worse.

Apep 2.0 was five times larger than the Chelyabinsk Rock.

Would it break up during its

10-second trip down through the atmosphere,

or would it pierce right through?

The planetary defense team ran simulations.

As that comes through Earth's atmosphere,

some of that hot air can get into the cracks.

[Rowe] Friction and pressure would heat Apep 2.0's

surface to thousands of degrees Fahrenheit.

At those temperatures, even rock burns.

We would see this flaming monster

of death coming racing through our atmosphere.

There are gonna be pieces of debris vaporizing

and coming off of it.

So you get these flashes of light that happen

one after another-- pop, pop, pop, pop, pop, pop, pop,

as these things are blowing up.

[Rowe] The computer simulations

showed that the extra bulk of

Apep 2.0 would stop it from blowing up.

Some of the asteroid would blast away,

but most of the space rock

would reach the Earth's surface.

So that close to the actual impact,

we pretty much just had to hunker down and take it.

[Rowe] The prospects for New York City were grim.

It was facing annihilation.

[Rowe] October 2029.

Three weeks to impact.

For the citizens of the New York metropolitan area,

there was only one goal-- Get out of the firing line.

Now we had to have

the plans in place to evacuate these cities.

It was a major emergency for New York and its citizens.

Time to move out of the way.

[Rowe] To work out who should evacuate and to where,

Scientists ran detailed projections

of the potential blast area.

There's an ellipse there that we call the hazard ellipse that

says somewhere in this area is where the asteroid will hit.

That means there's a little wiggle room

and a range of areas that are in danger.

[Rowe] Based on the hazard ellipse projections,

the government issued evacuation orders

for the tri-state area,

and as far south as Philadelphia.

It was the biggest evacuation in US history.

Millions were displaced.

It was physically horrific.

I live in the New York metropolitan area.

It was horrible for me and my family and my friends,

but we can't just sit here and cross our fingers and hope that

we don't get struck.

[Rowe] The freeways out of the city were jammed.

Trains were packed.

Over 23 million people evacuated,

leaving behind a deserted city.

Computer models show that the epicenter

of the strike would be Manhattan.

The blast would reduce the city to rubble and ash.

There would be a one-mile-wide crater resulting from it,

so deep that it would actually take

the entire subway system and turn it upside down and lay it

onto the rim of the crater.

You would have a magnitude 5 earthquake

at even six miles away from that,

and there would be a big air blast,

400-mile-an-hour winds.

Something as light as a pencil could be a lethal weapon

when picked up by a shock wave like that.

As the crater is blasting out and excavating itself,

there would be little blobs of molten rock that get thrown out

in this wave, going faster than the speed of sound,

Like drops a fiery rain,

if you will, landing back miles away from the crater.

[Rowe] The city would be on fire.

So, um, there's just no upside to this.

There's nothing good.

It's just all from bad to horrific.

[Rowe] But New York is by the ocean.

What would happen if Apep 2.0 hit the sea?

Detailed simulations have revealed two very

different outcomes

for an asteroid hitting the ocean at high speeds.

SUTTER: If a giant asteroid strikes the deep ocean,

less than 1 percent of its energy

gets converted into waves.

Those waves quickly disperse.

They quickly lose energy as they travel.

By the time they reach the coast, it might just be

a little ripple,

you might not even be able to surf on it.

[Rowe] If the asteroid hit shallow coastal waters,

it could cause significant damage along the shoreline.

If an asteroid, the size of Apep hits the continental shelf

where the water is relatively shallow,

then it could potentially cause a tsunami.

[Rowe] But that would just be the start of the problems.

With a shallow water impactor,

huge amounts of steam are generated basically by

the energy of that impactor vaporizing all the water.

Well, all the water is then put up into the atmosphere,

and water is a really good greenhouse gas.

So you have warming from the launch of water

up into the atmosphere.

You have cooling from all of the ash and dust.

[Rowe] A short bout of warming

would be followed by a brutal winter.

Crops would fail.

This impact has so many horrible follow-on consequences.

That tells us how difficult it would be to--

to rebuild from an event like this.

[Rowe] The eastern seaboard

would suffer a serious economic downturn.

It would take decades to recover.

November 3rd, 2029.

One day until impact.

The space rock was just 400,000 miles away,

and traveling 13 times faster than an F-15 fighter jet.

It was first a dim star, and then a brighter star,

and then in the hours before, you can actually see it

approaching the Earth.

[Rowe] New York looked outmatched.

It looked like Apep would win,

but this was not the end of the game.

Earth had one final card to play.

[Rowe] November 4th, 2029.

The 300-foot Apep 2.0 reached Earth.

The space rock pierced our

atmosphere and hurtled towards the surface.

Then the asteroid passed over Manhattan,

over Brooklyn,

and over Coney Island.

It hit deep ocean, 350 miles off the coast.

Apep 2.0 missed New York.

But how?

Our 7-year battle with the asteroid

resolved in a matter of seconds

thanks to orbital dynamics.

The orbit of the asteroid and the orbit of the Earth

and the way the Earth spins in this great cosmic ballet

means that

a few seconds earlier or later makes the difference between

hitting the ocean and hitting land.

[Rowe] Earth rotates at 1,000 miles an hour

and orbits the sun at close to 65,000 miles an hour.

Apep orbited at 40,000 miles an hour,

but Apep 2.0 traveled fractionally slower.

The impact of the DAAFE mission that sheared off

the 300-foot chunk of rock had also slowed it down.

Slowing down Apep

changed when it's going to intersect the Earth.

So New York spun out of the crosshairs.

[Rowe] Apep 2.0, hit the ocean and exploded,

breaking up instantly.

The strike threw up a wall of water into the air,

followed by huge clouds of steam.

The impact created small surface waves that quickly

died away.

It's like doing a gigantic interplanetary belly flop.

It evaporates, it obliterates, and it generates

an enormous amount of steam, and it sets up shock waves.

All that energy is still released,

but the ocean is capable of absorbing it.

[Rowe] New York dodged the bullet and escaped unscathed

thanks to the dedication, ingenuity,

and enterprise of a global team of scientists.

Apep was an imaginary asteroid,

but there are many potentially hazardous space rocks out there.

Thankfully, this was a fictional scenario.

It's a thought exercise, but it's informed by our real,

actual knowledge we've gained over the years of dealing with,

you know, potential close approaches and the hazard from

real asteroids that we actually know about.

Asteroid research is a good insurance policy

for our species.

Hopefully we will never need to carry these things out

for real.

[Rowe] Large asteroid strikes are rare,

but we cannot be complacent.

The most important thing to do in planetary defense

is to find them early.

If we find them early, we have a chance to predict

the possible impacts and we have a chance to mitigate them.

[Rowe] Our technology is improving,

so we can detect incoming space rocks earlier,

but we need to be vigilant,

because the threat from asteroids is not going away.

Apart from climate change,

asteroid strikes are, in my opinion, the most dangerous

thing to life on Earth.

[Plait] A lot of the times the question I get is,

"What are the chances of this happening?"

And they don't like the answer because I say 100 percent.

It takes time.

It may not be for a week, a month, a year, a century.

But studying these asteroids informs us on

what we can do to prevent an impact.

There are a lot of natural disasters that we can do

nothing about-- earthquakes, hurricanes,

that sort of thing.

Here is something way more devastating

than any of those, and we can prevent them.

So we have to keep our eyes on

the prize and our eyes on the skies.