Original subtitles

Sixty-six million years ago,

this asteroid crashed into Earth

and wiped out

most of the life on our planet.

Including the biggest,

baddest things

that ever roamed the planet.

Yeah, dinosaurs.

If a rock this size hit us today,

well,

humans would be

on the brink of extinction.

Today,

we look at the five

deadliest asteroids to hit

Earth -

Either in the past

or in the not-so-distant future.

And we’ll slam them into Earth,

all at the same time.

Spoiler alert: Earth does

not win.

We'll start

with the smallest rock on our list.

The Barringer asteroid.

And then we'll

build up to an asteroid

that was much,

much more massive

than even the Chicxulub

that wiped out dinosaurs.

But before we get there,

here's the thing about space rocks.

They aren't some rare event.

They barge in from space

and hit Earth all the time.

Most of these rocks

are tiny meteoroids,

just a few grams in weight.

But they come in fast.

These small meteoroids

slam into Earth

at tens of kilometers per second.

Lucky for you,

they burn up almost instantly

thanks to our planet's home

security system, our atmosphere.

But sometimes, Earth gets hit

by a way more serious rock.

And the damage can be catastrophic.

Let me take you

back - 50,000 years into the past.

Earth was deep in its last Ice Age.

When suddenly,

a large space

rock entered the atmosphere.

This is the Barringer asteroid.

For millions of years,

it was minding its own business

in outer space.

And then, suddenly,

on a perfectly ordinary day

in what we now call

northern Arizona in the U.S.,

this 50-meter-wide chunk of iron

and nickel,

that’s 165 feet in diameter,

this chunk came

tearing into Earth’s

atmosphere at over

15 km/s (9 mi/s).

Just seconds later,

it slammed into the ground

with a force so powerful,

it was like

setting off a line

of nuclear bombs.

The shockwave flattened everything

as far as the eye could see,

and the asteroid left

a massive crater to remember it by.

Now, what if this asteroid

hit us today?

Well,

it would be just as devastating.

If the Barringer asteroid

hit Earth near a major city,

that would be total destruction.

This 300,000-ton bullet from space

would explode

with the energy

of 10 megatons of TNT.

It would flatten

skyscrapers in an instant,

shattering glass for miles.

Even if you weren’t at ground

zero, that’s

the exact point of impact,

you’d feel the power

of its shockwave.

The blast would deafen

you, and the heat would,

well, fry you.

The ground would shake as if a

magnitude 7.5

earthquake had just hit.

The Barringer wouldn’t

be a world-ending asteroid.

But it would change the world

for everyone nearby.

Now, since

we want to keep things

exactly like they happened on Earth

50,000 years ago,

this space rock would hit

exactly where it hit

then, in the middle of a desert.

But As long as you’re

not a tourist

or a hiker

exploring the arid

expanse of Arizona,

you'd be fine.

Still,

this new Barringer

asteroid would leave a new crater,

a crater that’s

big enough to fit Burj

Khalifa inside of it.

This is what today's impact

would look like.

If

watching the impact

from the nearest town

over, Winslow, Arizona,

you'd see the kilometer-high

cloud of ash and fire

rising from the impact site.

About a minute after impact,

just as you think you're safe,

the sonic boom would reach you,

knocking you to the ground

and shattering

all windows around you.

It would be huge, but still,

not a leveling-a-city-to-the-ground

kind of impact.

Okay,

while the Barringer asteroid

raised a plume of smoke

and ash in Arizona,

something bigger and deadlier

is about to smash

into South America.

BARRINGER ASTEROID DEMOLISHES ARIZONA

Arizona treated to brightest firework since the Cretaceous.

If the Barringer asteroid did hit Earth today,

those are two fictional headlines you might see in the news.

And both give a vastly different understanding of what happened.

In today’s landscape, finding out the truth

of anything can be difficult.

That’s where Ground News comes in.

It’s a website and app that helps you cut through the noise

and see how hundreds of news outlets are reporting

on the same story — all in one place.

One of its most useful features is the Interest Pages,

which let you follow news stories in categories you care about.

Like science, technology, or politics.

And when you find a story that catches your attention,

Ground News helps you understand the bigger picture

by showing you how coverage differs

across the political spectrum, how factual each source is,

and what context you might be missing.

The bias comparison feature summarizes the bias for left,

right and center publications.

Do you remember when scientists found

bio-markers for life on K2-18b?

We sure do, we sent Chase there to find out more.

Unfortunately, his results were about

as varied as the news publications’.

More than 400 news stories were published

regarding K2-18b.

This article would have you believe

there is a 100% guarantee of life on the planet,

while this article highlights that

the scientists discovered ‘hints’

and are still mostly skeptical at this stage.

Coming across only one of these articles,

you might believe it’s either a sure thing

or sensationalistic journalism.

But with Ground News, you can filter for bias

and quickly glance at a publication's Factuality Score.

Understanding the context of who

is reporting on a topic will help you understand

the truth of what actually happened.

If this sounds like something that would help you

sort through the noise and hone in

on learning about what really matters to you,

visit ground.news/wif.

Or scan this QR code.

Subscribe now and get a 40% discount

on their unlimited usage Vantage Plan.

Understanding the history, context

and factuality surrounding each news event

can be extremely beneficial in today’s landscape.

But the landscape of the ancient past

had entirely different, astrological problems to contend with.

Astronomers first

spotted Asteroid YR4 in December

of 2024,

using the ATLAS system in Chile.

And let me tell you,

this rock almost

gave us a heart attack.

By the way,

ATLAS stands

for Asteroid

Terrestrial-Impact

Last Alert System,

so that should give you an idea

of why this discovery

was so terrifying.

At first,

it looked like YR4

had a 3.1% chance of hitting Earth

on December 22, 2032.

Now, that may not sound like much,

but in

asteroid terms, that’s

alarm bells territory.

Scientists worldwide

scrambled to refine its orbit,

and as more data came

in, they brought that number down.

First to 1%,

and eventually,

to even less than that.

Now, it's

something like a 0.001% chance.

Yeah, but that's still more percent

than you ever want to hear.

Of course, here on What If,

we always

imagine the worst-case scenario.

So, fast-forward to 2032.

Cue the impact.

The thing you need to

know about YR4?

It's big.

At a length of about 60m (200 ft),

it's about the size

of a jumbo jet.

And this intruder

from space wouldn't

even need to touch the ground

to cause serious damage.

Yeah, instead of directly

hitting Earth,

YR4 would explode overhead like

the Tunguska event

did in 1908,

in a remote region of Siberia.

This rock would explode

like a deadly firework

and level the city beneath it.

Buildings would collapse,

and only reinforced

bridges would remain standing.

Barely.

Predicting exactly

where the asteroid would hit

is difficult.

We have to take into account

Earth's orbit,

the asteroid trajectory,

and speed for starters.

It might land

somewhere in the ocean.

wouldn't it be more epic

if it landed on land?

Say, in northern South America?

Yeah, our deadly

space traveler

would land in Bogota, Colombia.

Bogota, Colombia, is a city of over

7 million people,

tucked high in the Andes.

But its elevation wouldn’t save it.

The skies over

Bogota would light up,

as if the Sun had suddenly moved in

for a close-up.

Then, about 10 km above the city,

that's about 6 mi,

YR4 would detonate

in a massive airburst.

It’d release the energy

of about 15 megatons of TNT.

That's 1000

more than the bomb

that was dropped on Hiroshima.

The shockwave would rip

across the city in seconds,

flattening buildings,

snapping power lines,

and throwing vehicles

into the air like toys.

If you were caught outside,

you'd be blinded by the flash,

then knocked to the ground

by the blast wave seconds later.

Fires would break out

across entire neighbourhoods

and glass

and debris

would turn into deadly shrapnel.

The destruction wouldn’t

stop at Bogota’s city limits.

The Andes would echo

with the sound of the explosion.

Dozens of kilometers away,

windows would shatter.

Nearby towns would feel like

they were hit

by a massive earthquake.

Power would be out

for millions of people.

Communications would fail.

This is where the chaos kicks in.

But since the asteroid didn't

actually strike the ground,

there wouldn't be a crater.

Instead,

the city would be marked

by a burned, flattened zone

where the blast hit hardest.

It wouldn’t be the end of humanity,

but for South America,

it would be remembered

as the day of scorched earth.

Now, if something like YR4

was on a collision course with us,

we wouldn't

be completely defenseless.

NASA has already tested

a planetary defense

strategy called DART,

that's short

for the Double Asteroid

Redirection Test.

The idea

isn't to destroy the asteroid,

but just to redirect it

while it's still in space.

NASA tested it in 2022

by deliberately slamming

a spacecraft

into an asteroid moon

called Dimorphos.

It worked.

When you're dealing with asteroids,

even a tiny course

correction years in advance

can mean the difference

between a harmless flyby

and a direct hit.

I'd still feel safer

if YR4 had a zero chance

of hitting us in the first place.

But But it looks like

it might just hit the Moon instead.

What a relief.

And as if South America didn't

have enough to deal with,

another big strike

is coming its way.

Oumuamua is a

special rock on this list.

Because this was the first-ever

interstellar object

that we saw enter

from interstellar space.

Like, it

came from outside our Solar System.

And it was weird.

Oumuamua isn't

your average round asteroid.

It's what scientists

and I call cigar-shaped.

It's ten times

longer than it is wide.

We've never seen anything like it

until we saw this in 2017.

At first, it looked like a comet

because it accelerated

in a strange way,

almost like it was being pushed.

But scientists would never see

a comet like tail,

which made things awkward.

It could be a fragment

of a larger rock.

It might have exotic ices

in its composition,

like hydrogen ice or nitrogen ice.

Or it may even be an ‘alien-made’

object.

Something they've sent to explore

our little planetary cluster.

Either way, this elongated rock

is about to slam into us.

First,

Oumuamua would hit

the top of the atmosphere,

speeding at 20 to 26 km/s

(12-16 mi/s).

For a moment,

it would look like

there was a second

Sun over the Amazon.

Hey, somebody give this guy

a speeding ticket.

But in just a moment,

it'll crash into the rainforest

with about one gigaton of energy.

A new crater

will be torn into the basin.

A crater from this monster

would be no joke. About

4 km, or 2.5 mi, across and

600m, or 2,000 ft, deep.

Everything inside

that ball would vaporize.

The shockwave would race outward,

snapping trees like matchsticks

and lighting the canopy on fire.

From above, the world’s green lung

would turn into a ring of brown

and black.

Towns far

beyond the horizon would feel

the shockwave

as a hard shove and a long roll.

Ash would be falling from the sky.

For days,

it would be snowing charcoal.

Oumuamua

launching itself into Earth

wouldn’t cause

an extinction-level event,

but it would definitely be a blast

that the planet would remember.

The Amazon

River would run

hot and cloudy with ash.

Air travel would be diverted

for weeks.

And across the northern part

of South America,

crops would get less light

under an ashy sky.

We’re

not at the level

of dinosaur extinction,

but we’re getting there.

Over in Mexico,

the big

celebrity herself

is about to destroy everything.

This is the most famous

asteroid out there.

The boulder with the smolder.

The world-ending Chicxulub.

66 million years

ago, this rock,

or more like ‘this mountain,’

smashed into Earth

on the coast

of the Yucatan Peninsula in Mexico.

And I'm not exaggerating

when I say it was a mountain.

Chicxulub measured at least 10

km, that's 6 mi, in diameter.

That's

bigger -

much bigger, than Mount Everest.

After Chicxulub hit,

Earth was never the same.

First came

the fireball

that ignited the forests.

Then the shockwave

that circled the globe.

A lot of dinosaurs

were killed immediately.

But not all of them.

After the great

fireball came the great blackout.

The Chicxulub impact

spewed dust

and ash into the sky,

blocking sunlight.

For years after the impact,

our planet was plunged

into darkness.

Many plant species died,

and when the plants went,

everything that fed on them

went, too.

This was the most recent extinction

event in Earth's history.

The dinosaurs never stood a chance.

But now,

this massive monstrosity

is coming to end you.

Yeah,

if this devastating rock

were to hit the Yucatan

Peninsula today,

it wouldn't be the

dinosaurs going extinct.

It'll be you.

At first, a bright star

appears in the sky out

over the Gulf of Mexico.

It's too bright and too fast.

In less than a minute,

it would grow to the size

of a blazing sun.

Then, the impact.

The blast would vaporize everything

in the vicinity.

The ground would shake

for hundreds of kilometers

with the energy of a magnitude

ten earthquake.

Coastal towns

would turn to white hot

ash, and skyscrapers of Cancun

would collapse from the shockwave.

Cue the massive tsunami.

Within hours of the impact,

not one,

but multiple tsunamis

would be roaring across

the Gulf of Mexico.

Walls of water 100 m (330 ft)

high would

slam into Florida,

Cuba and Central America.

Less than 48 hours later,

these huge waves

would reach Australia.

Back in Mexico,

fires would rampage.

There'd be a

thick, choking cloud of dust

and ash and sulfur everywhere.

If somehow you survived

the impact,

you wouldn't be able to breathe.

Look,

the dinosaurs

didn't survive this story

66 million years ago.

And if Chicxulub were

to strike again today,

humanity wouldn't either.

Not because

of the first flash of fire, though

that alone would cause

a lot of casualties.

But because of the long,

cold night that follows.

In the weeks after Chicxulub,

the world would fall silent.

Smoke and dust

would block out the Sun.

Earth would be plunged

into a cold twilight.

Soon,

the food chain

would begin to collapse.

Famine would spread faster

than relief could keep up with it.

Just a few months

in, humanity

would be living in chaos,

struggling to survive.

Years later,

if you were still around

in some sort of Last of Us

scenario,

you'd be walking

through an unrecognizable world.

Forests would be gone, coastlines

redrawn, and entire species

would have vanished forever.

Okay, that was devastating.

The smaller asteroids on this list

we could recover from,

but this one?

Yeah, it's not looking

good for humanity.

Or any aninty.

Animal-anity, plant-anity...

But wait, this wasn't

even the biggest impact?

It gets worse?

What's worse than that?

OK, this one is from a really,

really distant past,

when Earth was young

and very different from the Earth

you know.

Let’s go back

3.3 billion years ago.

This it

the Paleoarchean

era of early Earth.

This is when our planet

was mostly a waterworld,

with a few early continent-like

landmasses scattered around.

There was barely any oxygen

in the atmosphere,

and with no ozone layer,

the Sun bathed early Earth

in lethal radiation.

But that’s okay

because there was basically

no complex life here.

Only some simple

single-celled organisms

like cyanobacteria,

drifting in the ocean.

Then came S2.

This space rock was

absolutely, devastatingly massive.

Yeah, about

200 times

more massive than Chicxulub, so,

if you can imagine,

the impact was enormous.

S2 plunged

into the shallow seas near

what's now called South Africa,

and it changed the world forever.

But it was actually kind of

good for Earth.

Sure, there were humongous

tsunamis ripping apart

coastlines across the planet

and stripping debris

from the ocean floor,

tossing it into the atmosphere.

The surface

layers of the oceans boiled away

and heated up the atmosphere.

Molten rock rained from the sky.

But this was the kind of shake-up

Earth needed.

You see, this impact

stirred up

iron from the depths of the ocean.

This was a good thing.

Because now,

the seas

suddenly became full of nutrients.

All kinds of bacteria

and microorganisms

went through a baby boom.

After the impact,

early life

really started to flourish.

But that doesn't mean

this massive impact

would be good for us today.

Yeah, if S2 hit

near South Africa today,

it would be game over

for all of us.

I could stop right there,

but I’ll give you some details.

A fireball

the size of a continent

would rise into the sky.

As S2 violently smashed into Earth,

it wouldn’t just vaporize

water and rock.

It would tear the seafloor apart.

Yeah, this impact crater

would stretch for hundreds

of kilometers.

Earthquakes 100 times stronger

than anything

recorded in human

history would rip across the globe.

And after that, well,

you know the drill.

Tsunamis, a barrage

of flying molten

rock,

blocked sunlight, the

collapse of ecosystems.

Followed by extinction.

Of us.

All of us. Following this,

Earth would change again in ways

we can’t even predict.

A total reset.

You for sure

are not surviving this one.

Now, if only 1 or 2 of these

asteroids hit Earth

at the same time,

we could still make it.

But add Chicxulub

and S2 into the mix,

and it doesn't matter

how many relatively small impacts

you survive.

No one survives meteorite S2.

So lucky for you

that you’re living today

and not in prehistoric times,

where you'd be constantly

hiding, running,

being hunted down

by the terrifying

creatures of the past.

Unless...

Well, that’s a story for

another WHAT IF.