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 a fictional asteroid strike

to prepare for the worst-case scenario.

November 4th, 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?

New York City. November 4th, 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.

As it comes through the atmosphere,

we would see something as bright as the sun,

getting brighter and brighter and brighter.

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.

When it impacts, it will deliver more energy

than 1,000 Hiroshima nuclear bombs.

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,

of how horrible it would be.

This is beyond the worst disaster the world would have ever faced.

There's nothing in our history that would have done

this much damage so quickly and so devastatingly.

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 the heavens Greg Leonard

drives to Mount Lemmon Observatory near Tucson.

He is on the hunt for asteroids and comets.

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.

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.

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.

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.

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.

We had 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.

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.

Orbits are a little like roads. Right?

You've got a path that something follows and they can intersect.

You can have a crossroads.

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.

That's the danger from asteroids.

The team of scientists tracked the asteroid for four months.

Over time, you can build up observations.

You can gradually narrow down the possible number of orbits

and then determine whether there is any chance of a future impact.

But the asteroid is orbiting the Sun. The Earth is orbiting the Sun.

There's this dance going on.

Sometimes, the asteroid is near the Earth.

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.

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.

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 would have chaos, destruction and death.

A catalog of devastation to be unleashed on Earth,

but just how bad would the impact be?

January 2023.

Asteroid Apep was on a collision course with Earth.

Step 2 in our planetary defense?

Know your enemy. 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 referred to as a PHA.

A Potentially Hazardous Asteroid.

We're talking about something that is a third of a mile across.

This is enormous.

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

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 three or four miles across and 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 miles an hour wind,

radiating out, levelling 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 survive that, then there's going to be the blast wave

that will pulverize anything in its path.

To build an accurate simulation, the scientists used more than

size and mass, they also studied its composition

and the speed of its orbit.

You need to know what an asteroid is made of,

the speed of that asteroid

and how large it is in order to understand

will it make it through Earth's atmosphere

and what might the impact effects be?

Asteroids vary in composition and structure.

Some are loose collections of small rocks.

Others are 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.

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.

The meteor that made it was only about 150 feet across.

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.

More common are rubble piles.

Loose collections of small rocks, held together by gravity.

A rubble pile is the perfect name for them. You can think of them

as like, literally, a pile of stuff

out of a dump truck in your driveway.

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.

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 break-up of an asteroid in the upper atmosphere

is pretty devastating.

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

Flattening buildings and breaking windows.

There are gonna be mass casualties from an event like that,

due to just the injuries from flying glass and debris.

To discover what type of asteroid Apep belonged to,

the planetary-protection team

train their telescopes onto the space rock.

The 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.

C-type asteroids pose another problem

for the planetary-defense team.

The C-type asteroids, like Apep, are very difficult to see

out there, in the sky, they are very, very dark.

They're not reflecting a lot of light back to us.

It's almost as if they have these invisibility cloaks,

preventing us from seeing them sneaking up on us.

This C-type invisibility cloak made detection difficult.

But our space tech was up to the job,

collecting the crucial intel needed for an Apep-damage projection.

Apep's size, mass and composition told us it would punch though

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.

Scientists calculated how much energy Apep,

weighing in at 123 million tons

and travelling at 40,000 miles an hour, would transfer into the Earth.

So what kind of energies are involved here?

An 1,800-foot diameter asteroid.

It's 112 million tons.

It was travelling at 40,000 miles per hour.

That's something on the order of 10 to the 19 Joules of energy.

A one followed by 19 zeroes.

1.8 x 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.

A strike this large would affect the whole planet.

This would have a global impact.

We would have to deal with the fall-out, the literal fall-out

from this event for potentially 1,000 years.

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.

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.

June, 2023.

A large asteroid was headed towards Earth.

It was predicted to strike on November 4th, 2029.

To protect our planet,

a team of scientists plan to deflect the asteroid.

A 1,800-foot-wide asteroid was headed towards the Earth.

We needed it to go in, literally, any other direction.

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.

If we 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.

Sounds simple.

Send up a rocket with a robotic space probe,

travel millions of miles,

then knock Apep away from Earth.

Piece of cake!

In the movies, when there's a threatening asteroid that's found,

there is always a rocket on the pad ready to go after that.

That's not the case in real life.

It takes years to design the mission,

to build the satellite, to launch it.

Then it has to get there

and that might be millions of miles away from Earth.

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.

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 is in.

The lessons learned from DART would inspire a new mission.

November 2025.

We launched the DAFE 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 and an exact point in space,

it's really the ultimate bull's-eye.

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

launched from the other side of the continent.

November 2028.

After three years in space,

DAFE arrived at Apep.

This was our last chance. This was our only chance.

The kinetic-impactor smashed into Apep at 14,000 miles an hour.

On Earth, telescopes and radar track the collision.

Did it work?

Did we push the asteroid off-course?

At first glance, the mission worked. We deflected Apep away from us.

It looked like the mission worked.

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.

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.

The important thing we needed to know, was it going to hit us?

And, if so, where is it gonna hit us?

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.

A smaller chunk headed for New York City?

This was the worst-case scenario.

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 had worked inArmageddon.

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.

Computer simulations revealed that even the world's largest

nuclear weapon had only 1% 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.

Fortunately, thanks to the DAFE mission,

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

Could we blow this 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.

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.

They cannot be tested in space, according to international law.

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.

The people in Chelyabinsk were very lucky, because of that.

The 60-foot-wide Chelyabinsk asteroid was rocky, like Apep.

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."

But all of those molecules

actually exert pressure on the front edge of the asteroid,

slowing it down and heating it up.

The rock heated up and began to crumble and explode,

as it came through.

The mid-air explosion, called "an air burst",

released more energy than 440,000 tons of TNT.

The shockwave travelled 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 ten-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.

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! As these things are blowing up.

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.

The prospects for New York City were grim.

It was facing annihilation.

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.

To work out who should evacuate and to where, the 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.

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.

The freeways out of the city were jammed.

Trains were packed.

Over 23 million people evacuated.

Leaving behind a deserted city.

Computer models showed 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-five earthquake

at even six miles away from that

and there would be a big air blast and 400 miles 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 of fiery rain, if you will,

landing back miles away from the crater.

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.

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.

If a giant asteroid strikes the deep ocean,

less than 1% 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.

If the asteroid hits 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.

But that would just be the start of the problems.

With a shallow-water impact,

huge amounts of steam are generated,

basically, by the energy of that impactor vaporizing all the water.

All the water is then put up into the atmosphere.

Water is a really good greenhouse gas.

So you have warming from the launch of water up into the atmosphere

and you have cooling from all of the ash and the dust.

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 rebuild from an event like this.

The Eastern Seaboard would suffer a serious economic downturn.

It would take decades to recover.

As the asteroid edged closer to Earth,

observations would normally be carried out by

the Arecibo Radio Observatory.

The telescope's radar detectors could give us

vital, last-minute intel on the space rock.

You emit a series of pulses to the asteroid. You have to know where

the asteroid is, by the way, because it's a focused beam.

And the asteroid will reflect those radar signals

and you pick up the echoes.

But, back in December, 2020,

Arecibo's giant radio disc collapsed.

A key line in our defenses was suddenly out of action.

Losing Arecibo was a disaster for us, in planetary defense.

Arecibo allowed us to do spacecraft-level reconnaissance

of near-Earth asteroids.

We could see them. We could see the details on their surfaces.

It allowed us to very precisely track where they're going

and follow up the telescopic discoveries.

So we can no longer use the Arecibo data.

We do have the Goldstone Antenna, however, which is a little smaller,

in the Mojave Desert, in California.

It is able to bounce radar signals off the asteroids.

We do use that a lot to measure distances to asteroids.

November 3rd, 2029. One day until impact.

The space rock was just 400,000 miles away.

And traveling 13 times faster than a F-15 fighter jet.

It was, first, a dim star

and then a brighter star and then, in the hours before,

you could actually see it approaching the Earth.

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.

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 seven-year battle with the asteroid was 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.

The 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

travelled fractionally slower.

The impact of the DAFE mission that sheared off

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

Slowing down Apep changed when it was gonna intersect the Earth,

so New York spun out of the crosshairs.

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 shockwaves.

All that energy is still released,

but the ocean is capable of absorbing it.

New York dodged a 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, a thought exercise,

but it's informed by our real, actual knowledge,

that we've gained over the years of dealing with

potentially close approaches

and the hazards 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.

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.

If we talk about the large ones, larger than, you know, half a mile,

then we know that there are about 940, in total, of that population.

What that means is that we've discovered

96% of that size asteroid,

so we're doing really well with the large asteroids.

But the smaller the asteroids get, the harder they become to track

and some of the smaller ones

could still cause us damage.

So we are adding the Near-Earth Object Surveyor to our arsenal,

to find the smaller threats

that we might otherwise miss.

NEO Surveyor is a critical mission.

It's an infrared camera.

In infrared, asteroids are easier to see. They're brighter than they are

in visible light, so they jump out at you.

You can track them and that is the most important thing.

It will be sensitive enough that it can discover these asteroids

that are 140m,

460 feet and larger

and to find enough of them, over its five to ten year lifetime,

that we will reach the 90% goal that Congress has assigned us.

So we're getting there, but we have more work to do.

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.

A lot of the time, the question I get is,

"What are the chances of this happening?"

And they don't like the answer, because I say, "100%."

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, but 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.

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