Space's Deepest Secrets

NASA's Osiris-Rex is on a mission

to intercept a giant space rock

and crack the mysteries of a potential killer asteroid.

If this mission sounds familiar,

it's because it's like something right out of a Hollywood script.

Can Osiris-Rex help to stop this asteroid

colliding with earth in the 22nd century?

Are asteroids dangerous? Well, ask a dinosaur.

Can it unlock how asteroids kick-start life

on planets like our own...

Turns out the whole story of our existence,

our origins, is wrapped up in those space rocks.

...And reveal why they might be our ticket to other worlds?

They could be the key that enables us

to explore the outer solar system.

To find out, we take a ride

with one of NASA's most ambitious missions

to investigate a space rock in more detail than ever before,

to reveal how asteroids will rewrite the past

and forge the future of our solar system.

Over one million asteroids hurtle through space

between Jupiter and Mars.

They are the debris left over

from the violent birth of the solar system

4 1/2 billion years ago.

Many of these ancient space rocks contain a pristine record

of the conditions that existed before the earth was born.

Telescope analysis of asteroids

reveals that many of them carry organic material.

Astronomers think that the chemistry of this space soil

could unlock the secrets of how life

starts on a planet like earth.

Think about all the mysteries of how we got here,

how life began to evolve.

Is there any way you could actually have a sample

of what the early solar system is like?

Well, it turns out we can... In an asteroid.

But asteroids also pose a threat.

NASA has identified 9,000 asteroids

that are large enough to destroy a city

if they were to hit the earth.

Some asteroids are so big

they could wipe out all life on our planet.

Some of them would have energy associated with their impact

that could exceed the binding energy of the earth's crust.

That means after the impact,

the earth's crust would turn into an ocean of magma.

That would cause a global extinction event at all scales.

Now, I don't want to scare you, but they are out there.

How can astronomers unlock the secrets of the origins of life

from inside asteroids?

And can they solve the mystery of why some space rocks

end up on a collision course with our planet?

Telescopes struggle to see the details

of small, dark asteroids

against the vast blackness of space.

Astronomers must get closer

if they want to reveal the secrets locked inside asteroids,

as well as assess the threat that space rocks pose.

So NASA launches Osiris-Rex.

It is the first U.S.-led mission

with the aim to return a sample of an asteroid to earth.

Engineers equipped the spacecraft

with a suite of special instruments.

These can map the geology of an asteroid

in unprecedented detail...

And then take a sample from the surface of the space rock

so that Osiris-Rex can bring it to earth

for scientists to study.

This is NASA's most ambitious asteroid mission.

The stakes are high.

These missions take decades to develop

and hundreds of millions of dollars,

not to mention the hearts and souls of thousands of people

who have dedicated their careers to this mission.

Building a robust and well-equipped spacecraft

is just one part of the mission.

Success depends on selecting the right asteroid

to intercept and study.

Out of the 18,000 asteroids close to earth,

which one should Osiris-Rex go visit?

Telescopes on earth analyze thousands of space rocks

to identify the perfect candidate.

Astronomers narrow down the list to just one.

The asteroid is called Bennu.

Bennu is a bulging space rock 500 yards wide.

It orbits the sun on a similar path to earth.

The asteroid has a slow and steady rotation.

This makes it easier for Osiris-Rex to get close.

It is dark in color,

a sign that this asteroid could contain organic material.

Such material will help scientists

solve why life thrives on earth.

And Bennu is second on NASA's list

of most dangerous space rocks.

This asteroid makes the perfect target for Osiris-Rex.

NASA had a lot of criteria

when they were trying to find the perfect asteroid

to send Osiris-Rex to.

Well, it turns out Bennu just snaps them off one at a time.

Osiris-Rex arrives at Bennu in December 2018.

The first objective for the spacecraft

is to find out just how much of a threat Bennu poses to earth.

When could this space rock hit our planet?

An asteroid the size of Bennu hits the earth

roughly, very roughly every 100,000 years.

Now, that's not like clockwork.

It could be a year from now,

or it might be a million years from now,

but over time, that's about how often it happens.

We know that Bennu is a danger to us,

but we don't know exactly how dangerous.

And that's why we have the Osiris-Rex mission...

To go there and figure it out.

A clue to unlock when Bennu could hit earth

lies in changes to the asteroid's trajectory

that happen each time it swings by our planet.

Bennu laps earth every 6 years.

Each time, there's a chance

it will pass through a gravitational keyhole.

This is a narrow corridor where earth's gravity

pulls the asteroid onto a dangerous trajectory.

Astronomers believe that Bennu

could pass through a gravitational keyhole

when it dives between earth and the moon in 2135.

If it does, it means there's then a 1-in-2,700 chance

that Bennu will collide with earth 50 years later.

1 in 2,700 might sound like really low odds,

but when you're talking about an impact

that could destroy a city,

it's worryingly high.

Astronomers need to know for sure

if Bennu will pass through a gravitational keyhole

and end up on a collision course with our planet.

But it's difficult for astronomers

to predict the future path

that an asteroid will take through space.

Telescope observations reveal that Bennu moves

around 300 yards closer to the sun with every orbit.

What is the mysterious force that drives Bennu

towards this center of the solar system?

And can it help scientists calculate

if Bennu will end up on a collision course with earth?

Osiris-Rex is on a mission

to return a sample from asteroid Bennu.

This space rock could collide with earth in the 22nd century

after an epic journey from the asteroid belt.

What is the mysterious force that pushes Bennu

ever closer to the center of the solar system?

Astronomers believe that the heat from the sun

unlocks the mystery.

Bennu makes one full rotation every 4.3 hours

as it flies through space.

Sunlight warms the surface of the asteroid.

As the heated rocks rotate away from the sun

towards Bennu's dark side,

they radiate their heat into space

on the asteroid's leading edge.

This gives the asteroid a tiny push backwards.

Astronomers call this process the Yarkovsky effect.

Like a low intensity thruster, it slows down Bennu

and allows the sun to pull it closer with every orbit.

The Yarkovsky effect is very small in any given moment,

but over a large amount of time,

it could actually have a big effect.

It's already moved Bennu from the asteroid belt

inward toward the earth.

Infrared cameras on board Osiris-Rex

measure how quickly the surface of Bennu

heats up and cools down.

This data will help astronomers calculate the influence

that the Yarkovsky effect has on Bennu's orbit around the sun.

This calculation could predict precisely if and when

Bennu will pass through a deadly gravitational keyhole.

Is it changing in such a way that it moves away

from one of these keyholes,

or is it going to pass through a keyhole,

moving it in a direction of a collision course with earth?

Rogue asteroids

have the potential to devastate our planet.

Osiris-Rex will help astronomers accurately assess

the threat that Bennu poses to life on earth.

But what secrets about the origins of life

are buried inside this space rock?

Scientists think that Bennu contains

ancient organic material

that could help solve the mystery.

If we look at Bennu, it's primordial,

it's pure, it's untouched, it's been out there by itself,

isolated from pretty much everything but sunlight.

This material could be older than the earth.

It probably is.

So if we want to understand how our solar system formed,

this is where we need to go.

Osiris-Rex photographs its first clue in January 2019.

This image shows the surface of Bennu ejecting particles.

Of all the amazing science and images

that have come back from the Osiris-Rex mission,

the absolute coolest one to me

is that Bennu is spitting rocks into space.