How to defend Earth from asteroids

What's six miles wide and can end civilization in an instant? An asteroid – and there are lots of them out there. With humor and great visuals, Phil Plait enthralls the TEDxBoulder audience with all the ways asteroids can kill, and what we must do to avoid them.

I want to talk to you about something

kind of big.

We'll start here.

Sixty-five million years ago --

(Laughter)

the dinosaurs had a bad day.

(Laughter)

A chunk of rock six miles across,

moving something like 50 times
the speed of a rifle bullet,

slammed into the Earth.

It released its energy all at once,

and it was an explosion
that was mind-numbing.

If you took every
nuclear weapon ever built

at the height of the Cold War,

lumped them together,

and blew them up at the same time,

that would be one one-millionth
of the energy released at that moment.

The dinosaurs had a really bad day.

OK?

Now, a six-mile-wide rock is very large.

We all live here in Boulder.

If you look out your window
and see Longs Peak --

you're probably familiar with it --

now, scoop up Longs Peak
and put it out in space.

Take ... Meeker, Mt. Meeker.

Lump that in there,
and put that in space as well.

And Mt. Everest. And K2.

And the Indian peaks.

Then you're starting to get an idea
of how much rock we're talking about, OK?

We know it was that big

because of the impact it had
and the crater it left.

It hit in what we now know
as Yucatan, the Gulf of Mexico.

You can see here,
there's the Yucatan Peninsula,

if you recognize Cozumel
off the east coast there.

Here is how big of a crater was left.

It was huge.

To give you a sense
of the scale ... there you go.

The scale here is 50 miles on top,
a hundred kilometers on the bottom.

This thing was 300 kilometers
across -- 200 miles --

an enormous crater that excavated
out vast amounts of earth

that splashed around the globe
and set fires all over the planet,

threw up enough dust to block out the sun.

It wiped out 75 percent
of all species on Earth.

Now, not all asteroids are that big.

Some of them are smaller.

Here is one that came in

over the United States in October of 1992.

It came in on a Friday night.

Why is that important?

Because back then, video cameras
were just starting to become popular,

and parents would bring them
to their kids' football games

to film their kids playing football.

And since this came in on a Friday,

they were able to get this great footage
of this thing breaking up

as it came in over West Virginia,
Maryland, Pennsylvania and New Jersey

until it did that

to a car in New York.

(Laughter)

Now, this is not a 200-mile-wide crater,

but then again, you can see the rock,
which is sitting right here,

about the size of a football,

that hit that car and did that damage.

Now, this thing was probably
about the size of a school bus

when it first came in.

It broke up through atmospheric pressure,

it crumbled, and then
the pieces fell apart

and did some damage.

Now, you wouldn't want that falling
on your foot or your head,

because it would do that to it.

That would be bad.

But it won't wipe out, you know,
all life on Earth, so that's fine.

But it turns out, you don't need
something six miles across

to do a lot of damage.

There is a median point
between tiny rock and gigantic rock,

and in fact, if any of you
have ever been to near Winslow, Arizona,

there is a crater in the desert
there that is so iconic

that it is actually
called "Meteor Crater."

To give you a sense of scale,
this is about a mile wide.

If you look up at the top,
that's a parking lot,

and those are recreational
vehicles right there.

So it's about a mile across,
600 feet deep.

The object that formed this
was probably about 30 to 50 yards across,

so roughly the size
of Macky Auditorium here.

It came in at speeds that were tremendous,

slammed into the ground, blew up,

and exploded with the energy of roughly
a 20-megaton nuclear bomb --

a very hefty bomb.

This was 50,000 years ago,

so it may have wiped out
a few buffalo or antelope,

or something like that out in the desert,

but it probably would not have caused
global devastation.

It turns out that these things
don't have to hit the ground

to do a lot of damage.

Now, in 1908, over Siberia,
near the Tunguska region --

for those of you who are Dan Aykroyd fans
and saw "Ghostbusters,"

when he talked about the greatest
cross-dimensional rift

since the Siberia blast of 1909,

where he got the date
wrong, but that's OK.

(Laughter)

It was 1908. That's fine.
I can live with that.

(Laughter)

Another rock came
into the Earth's atmosphere

and this one blew up above the ground,

several miles up
above the surface of the Earth.

The heat from the explosion
set fire to the forest below it,

and then the shock wave came down
and knocked down trees

for hundreds of square miles.

This did a huge amount of damage.

And again, this was a rock
probably roughly the size

of this auditorium that we're sitting in.

In Meteor Crater, it was made of metal,

and metal is much tougher,
so it made it to the ground.

The one over Tunguska
was probably made of rock,

and that's much more crumbly,
so it blew up in the air.

Either way, these are tremendous
explosions -- 20 megatons.

Now, when these things blow up,

they're not going to do
global ecological damage.

They're not going to do
something like the dinosaur killer did.

They're just not big enough.

But they will do global economic damage,

because they don't have
to hit, necessarily,

to do this kind of damage.

They don't have to do global devastation.

If one of these things were to hit
pretty much anywhere,

it would cause a panic.

But if it came over a city,
an important city --

not that any city
is more important than others,

but some of them we depend on more
on the global economic basis --

that could do a huge amount of damage
to us as a civilization.

So, now that I've scared
the crap out of you --

(Laughter)

what can we do about this?

This is a potential threat.

Let me note that we have not had
a giant impact like the dinosaur killer

for 65 million years.

They're very rare.

The smaller ones happen more often,

but probably on the order of a millennium,

every few centuries
or every few thousand years.

But it's still something to be aware of.

Well, what do we do about them?

The first thing
we have to do is find them.

This is an image of an asteroid
that passed us in 2009.

It's right here.

But you can see that it's extremely faint.

I don't know if you can see that
in the back row.

These are just stars.

This is a rock
that was about 30 yards across,

so roughly the size of the ones
that blew up over Tunguska

and hit Arizona 50,000 years ago.

These things are faint.

They're hard to see,
and the sky is really big.

We have to find these things first.

Well, the good news is,
we're looking for them.

NASA has devoted money to this;

the National Science Foundation
and other countries

are interested in doing this.

We're building telescopes
that are looking for the threat.

That's a great first step.
But what's the second step?

The second step is if we see one heading
toward us, we have to stop it.

What do we do?

You've probably heard
about the asteroid Apophis.

If you haven't yet, you will.

If you've heard about the Mayan
2012 apocalypse,

you're going to hear about Apophis,

because you're keyed in
to all the doomsday networks, anyway.

(Laughter)

Apophis is an asteroid
that was discovered in 2004.

It's roughly 250 [meters] across,
so it's pretty big --

bigger than a football stadium.

And it's going to pass
by the Earth in April of 2029.

And it's going to pass us so close

that it's actually going to come
underneath our weather satellites.

The Earth's gravity is going to bend
the orbit of this thing so much

that if it's just right,

if it passes through this region of space,

this kidney-bean-shaped region
called the keyhole,

the Earth's gravity will bend it
just enough that seven years later,

on April 13 -- which is a Friday,
I'll note -- in the year 2036 --

(Laughter)

you can't plan that kind of stuff --

(Laughter)

Apophis is going to hit us.

And it's 250 meters across,
so it would do unbelievable damage.

The good news is that the odds of it
actually passing through this keyhole

and hitting us next go-around
are one in a million, roughly --

very, very low odds.

So I personally am not lying awake
at night worrying about this at all.

I don't think Apophis is a problem.

In fact, Apophis
is a blessing in disguise,

because it woke us up
to the dangers of these things.

This thing was discovered
just a few years ago

and could hit us a few years from now.

It won't, but it gives us a chance
to study these kinds of asteroids.

We didn't really necessarily understand
these keyholes, and now we do,

and it turns out that's really important,

because how do you stop
an asteroid like this?

Well, let me ask you:

What happens if you're standing
in the road and a car's headed for you?

What do you do?

You do this. Right?
Move, and the car goes past you.

But we can't move the Earth,
at least not easily,

but we can move a small asteroid.

And it turns out, we've even done it.

In the year 2005, NASA launched
a probe called Deep Impact,

which slammed a piece of itself
into the nucleus of a comet.

Comets are very much like asteroids.

The purpose wasn't to push it
out of the way;

the purpose was to make a crater
to excavate the material

and see what was underneath
the surface of this comet,

which we learned quite a bit about.

We did move the comet a little tiny bit --

not very much, but that wasn't the point.

However, think about this:

This thing is orbiting the Sun
at 10, 20 miles per second.

We shot a space probe
at it and hit it, OK?

Imagine how hard that must be,
and we did it.

That means we can do it again.

If we see an asteroid that's coming
toward us, headed right for us,

and we have two years to go?

Boom! We hit it.

You know, if you watch the movies --

(Laughter)

you might think:

Why don't we use a nuclear weapon?

Well, you can try that,
but the problem is timing.

Shoot a nuclear weapon at this thing,

you have to blow it up
within a few milliseconds of tolerance,

or else you'll miss it.

And there are a lot of other problems
with that; it's very hard to do.

But just hitting something?
That's pretty easy.

I think even NASA can do that,
and proved that they can.

(Laughter)

The problem is, if you hit this asteroid,
you've changed the orbit,

you measure the orbit,

then you find out, oh yeah,
we just pushed it into a keyhole,

and now it's going to hit us
in three years.

Well, my opinion is: fine!

It's not hitting us in six months --

that's good.

Now we have three years
to do something else.

And you can hit it again.

That's kind of ham-fisted;

you might just push it
into a third keyhole or whatever,

so you don't do that.

And this is the part --

it's the part I just love.

(Laughter)

After the big macho "Grr ... bam!
We're gonna hit this thing in the face,"

then we bring in the velvet gloves.

(Laughter)

There's a group of scientists
and engineers and astronauts,

and they call themselves
The B612 Foundation.

For those of you who've read
"The Little Prince,"

you understand that reference, I hope --

the little prince lived
on an asteroid called B612.

These are smart guys -- men and women --
astronauts, like I said, engineers.

Rusty Schweickart, who was an Apollo 9
astronaut, is on this.

Dan Durda, my friend who made this image,

works here at Southwest Research Institute
in Boulder, on Walnut Street.

He created this image for this.

He's actually one of the astronomers
who works for them.

If we see an asteroid
that's going to hit the Earth

and we have enough time,

we can hit it to move it
into a better orbit.

But then what we do is launch a probe
that has to weigh a ton or two.

It doesn't have to be huge --
a couple of tons, not that big --

and you park it near the asteroid.

You don't land on it, because these things
are tumbling end over end.

It's very hard to land on them.

Instead you get near it.

The gravity of the asteroid
pulls on the probe,

and the probe
has a couple of tons of mass.

It has a little tiny bit of gravity,

but it's enough
that it can pull the asteroid,

and you have your rocket set up --

you can barely see it here,
but there's rocket plumes --

and these guys are connected
by their own gravity,

and if you move the probe
very slowly -- very, very gently,

you can very easily finesse that rock
into a safe orbit.

You can even put in orbit
around the Earth where we could mine it,

although that's a whole other thing;
I won't go into that.

(Laughter)

But we'd be rich!

(Laughter)

So think about this, right?

There are these giant rocks flying
out there, and they're hitting us,

and they're doing damage to us.

But we've figured out how to do this,

and all the pieces
are in place to do this.

We have astronomers
with telescopes, looking for them.

We have very, very smart people,

who are concerned about this
and figuring out how to fix the problem,

and we have the technology to do this.

This probe actually can't use
chemical rockets.

Chemical rockets provide
too much thrust, too much push.

The probe would just shoot away.

We invented something called an ion drive,

which is a very, very,
very low-thrust engine.

It generates the force a piece of paper
would have on your hand --

incredibly light, but it can run
for months and years,

providing that very gentle push.

If anybody here is a fan
of the original "Star Trek,"

they ran across an alien ship
that had an ion drive,

and Spock said, "They're very
technically sophisticated.

They're a hundred years
ahead of us with this drive."

Yeah, we have an ion drive now.

We don't have the Enterprise,
but we've got an ion drive now.

(Laughter)

(Applause)

Spock.

(Laughter)

So ...

That's the difference --

that's the difference
between us and the dinosaurs.

This happened to them.

It doesn't have to happen to us.

The difference
between the dinosaurs and us

is that we have a space program

and we can vote,

and so we can change our future.

(Laughter)

We have the ability to change our future.

Sixty-five million years from now,

we don't have to have our bones
collecting dust in a museum.

Thank you very much.

(Applause)