So right now in Washington, D.C. there's this

thing going on called

The Planetary Defense Conference.

That is actually what it's called.

At the beginning of the conference,

NASA administrator Jim Bridenstine said this,

This is not about Hollywood.

It's not about movies.

This is about ultimately protecting

the only planet we know right now to host life.

And scientists there are laser focused

on figuring out one thing,

how to dodge an asteroid that is

currently hurtling directly at Earth.

Here's the thing.

That asteroid, it's not real.

So why are these scientists pretending that it is?

To find out, we talked to one of them.

I'm Cathy Plesko.

I'm planetary scientist at Los Alamos,

and I use supercomputers to model what happens

when a asteroid or a comet hits the earth

and how to stop one from hitting the earth.

And so, just like you have a fire drill,

just like when you sit down on a plane

and they tell you about the oxygen masks

and all of that, we practice this every two years

because we learn from practicing.

We learn from our mistakes.

Why is this coming up now?

Right, it's like as you said, these event in

and of themselves, we expect to be pretty rare,

so why now?

We're doing this now because this is

the first time we've really been capable of doing this,

and we've been buzzed a few times.

So, you know, you can't deflect a tornado

or a hurricane right now.

You can't glue a fault shut so San Andreas

doesn't have earthquakes anymore.

We can't do that yet.

But with an asteroid or a comet

it looks like we're pretty much there.

There's some technology that needs to be

developed yet, and there's a few things

we still need to learn about how these objects

are composed and how they respond to

being hit by a kinetic impacter

or being obliterated by a potentially

standoff nuclear device or shot with a laser.

The things that we're looking at as mitigation techniques.

We still need to study that very carefully

and that's why we're doing a lot of this on computer,

it's because if it goes sideways,

I can push delete and go home for dinner.

So, it's a much better thing to do a lot of

this homework before it's an issue.

What are the actual chances of a Near-Earth Object

breaking through the atmosphere and actually

making impact here on the ground?

We actually get hit every night.

If you go and, go to a place where the sky is

dark and look up, you're gonna see meteors

even on a night when it's not a meteor shower.

And so we get this constant rain of space dust

coming at us all the time, so you have something

like the airburst that happened in Russia

a few years back.

Those happen maybe once every 70 to 100 years we think.

Maybe medium-sized like Meteor Crater happen

maybe every, like fifty, hundred thousand years.

Really big things, like the one that killed

the dinosaurs, every 100 million years.

Bigger than that, maybe only a couple of times

in the history of the planet.

Can you explain what happened in Russia in Chelyabinsk

and why that was unique?

They were actually very lucky.

The Chelyabinsk object, the meteorite that came in

was about 70 meters across at the top of the atmosphere.

It was vert fragile so it broke apart

and it actually exploded three times on the way down.

And part of the reason that it did that

was it came in at a very shallow angle

and it, so it had a longer path through

the atmosphere to deposit its energy

and sort of air-brake.

That could have been much, much worse for the people

living in Chelyabinsk if it had come in at

a steeper angle and had more of

its energy focused on the city.

They don't hit that often, but we live in a hooting gallery.

These things are whizzing passed us all the time.

So back in the '90s there was the Shoemaker-Levy 9 comet.

It went so close to Jupiter it got torn apart

into a bunch of different pieces,

but then came back and hit Jupiter,

and we watched that very carefully,

and people modeled that at the time.

People are still studying that event.

There was Asteroid Apophis that made a close approach

while I was in grad school and I will never

forget that day my whole life

because Apophis is a big object.

It's hundreds of meters across.

It's a rubble pile, so it's a challenging one to deflect.

In 2004 when it came by us, it was a very

close approach to the Earth, and it's orbit

was not very certain at the time,

and there was a particular point in space

that if the center of mass went through

this little one meter keyhole,

the Earth's gravity would have torqued on it enough

that it would bring it back around

to strike us in 2029.

So, we were sitting in lab that day.

We all skipped class and sat there frantically reloading

the NASA website waiting to see what that trajectory was.

Fortunately, for all of us, it did

not go through the keyhole.

It is not going to hit the Earth in 2029.

But it is coming back.

That was also a wake-up call in 2004,

and that's when a lot of these meetings kicked off.

And they've been building steam ever since.

Let's say this was not a drill

and, you know, we do detect a Near-Earth Object

and it is months away from wiping out a US state.

What, what what are some of our options?

What can we do to deflect it?

Months away is a really bad day,

and so, if you've got something with only a few months

warning, that's a tough one to deal with.

At that point you're looking at a lot of evacuation.

With maybe six months warning, you, if you're real lucky,

and there's some science mission or other spacecraft

that's getting racked and stacked and ready to go out,

you might be able to send some sort of nuclear device

with it but that's, that's a big reach

because you have to prepare that sort of mission

extremely carefully, and so six months might not be

enough time to turn that around even.

When we talk about short warning times,

we're talking about a decade.

It takes years to prepare a spacecraft,

to design it, to get it ready, to build it,

to field it, to launch it, and then it takes

years to get it out into deep space to where

it needs to be to do the deflection.

You're talking about something that's floating

out in space that's the size of the Empire State Building

potentially, and you've got to push that thing around

to get if off Earth's orbit.

And so let's say we do have a longer runway,

you mention using a nuclear device for example

to divert its course.

We have a bunch of options that we're considering,

and it's very dependent on what the context is.

What kind of object is it?

How big is it?

How soon is it coming?

And these are, of course, all hypotheticals.

For a nuclear device, you have two options.

Like roasting a marshmallow, you can either stick it

in the fire or either hold back and get

the lighter brown color on the marshmallow

depending on whether you like it crispy or not, right.

With a nuclear standoff burst, how close you are

to the object determines how much energy you're

gonna source into it.

And you vaporize a thin layer off the surface

and that come off and pushes it in the other direction.

If you need to destroy the object

and disperse the fragments then, for example

if it's something really, really big, like if

it were a kilometer across then you might need to do this.

Then you can actually detonate the nuclear device

much closer in and potentially destroy and disperse it.

No, other options, people are looking at lasers

as another option.

The challenge with that one, as they reported

so far, I'm not working, on this project, is

keeping the optics clean.

So you're flying through this cloud of vapor

that you're roasting off the surface

and it keeps just plating onto the surface of

your lens and gungs-up your laser.

So you have to have this very creative windshield

wiper to keep that clean.

Other options, there's a group in Europe that's looking

at using ion engines, where you have a spacecraft

that then has a double-ended ion engine,

and so you fly in and you park it next

to your asteroid, and you have one ion engine

that's pushing you toward the asteroid

and then you fire another one at the asteroid

and you embed the exhaust from your ion engine

into the surface and you have a very gentle push

that way, but of course that takes a very long time.

Another thing that's coming up is the DART mission,

which is a technology demonstration mission

that NASA's going to do in a couple of years,

where they're going to send a small spacecraft

out to a binary asteroid system, and so you've

got the big asteroid and you've got a little

moonlet going around it.

And they're going to change the orbit of the little moonlet

around the big asteroid.

So we're getting to the point where we're

doing these babyceps, engineering and tech demos

that are convincing us that maybe we can get there.

And, so those are sort of the primary candidates right now.

Got it.

Let's say, all of these diversion tactics fail.

Is there a difference between an imapct that

takes place on land verse an impact

that takes place in the water?

Earth is a water world so a lot of these things will

just hit the ocean.

At that point you're concerned about potential

atmospheric effects, but we can model that.

You just need to get people out of the vicinity

and let if fall potentially if it's small enough.

And it turns out based on research done by some

colleagues of mine about tsunamis

that it actually takes a pretty hard punch

to make a tsunami.

If something hits on land then it takes a much

smaller object to make a problem.

When I say big, I'm saying a city killer

is gonna be, like football field size,

so 100 meters, 150 meters by 250 meters.

If it's 100 meters and it's made of metal

you're gonna make Meteor Crater, and if Meteor Crater

were made today, Flagstaff ain't coming out alive.

So that's a city killer.

If it's something that's more fluffy,

more fragile then that's going to be an air burst,

so if that hit over a populated area, yeah,

that's gonna burn some houses down pretty badly.

That's gonna look like a multi-megaton nuclear attack

on that city just without the radiation.

Once you're up to a kilometer that's gonna

be a global disaster because that's going to kick up

a lot of gunk into the atmosphere, and it's

gonna change the climate in pretty bad ways at that point.

If you look back into the early 1800s,

I believe it was the 1820s, there was a super volcanic

eruption that put a bunch of ash up into

the upper atmosphere and locked out enough sun

that they didn't have summer in

the Northern Hemisphere that year.

Crops in the US failed.

There was famine.

It snowed in New England that summer in July.

And that's the sort of things we would see.

So there's big incentives to avoid that kind of impact.

Yes, there is, and fortunately

they don't happen very often.

So, that's why we're planning now because we

wanna have some thoughts on this.

We wanna have a plan before anything where to happen

and we're finally as a species at a point

where we're technically capable of thinking

about this, and so it's time to start doing our homework

because we don't wanna be writing this final paper

during finals week.

You know, we wanna have this solved before

we've got something coming at us.

This has been incredibly informative

and a little scary but that's OK.

Thank you very much.