Nova (1974–…): Season 40, Episode 24 - Asteroid: Doomsday or Payday? - full transcript
The asteroid that exploded over Siberia--injuring more than 1,000 and damaging buildings in six cities--was a shocking reminder that Earth is a target in a cosmic shooting range. From the width of a football field to the size of a...
Our planet is under attack
Our solar system
is full of deadly missiles
that could strike at any time
It's like cosmic roulette
You can't go on
playing a game of chance
and expect to keep winning
Killer asteroids
Trillions of tons of rock,
hurtling through space at tens
of thousands of miles per hour
Some are on a collision course
with earth
An asteroid has
more damage potential
than a nuclear bomb
of the same energy
65 million years ago,
a huge asteroid wipes out
much of life on Earth
But strikes aren't all
ancient history
In 2013, a much smaller asteroid
terrorizes this Siberian city
For many, this really was
a wake-up event
Now the race is on
to understand the danger
We know they're out there
When and where
will the next one strike?
Will it hit on a city?
I don't know
The point is
we have to find that out
We really need to upgrade
the search capability
We stand at a crossroads
Only now do we have the ability
to identify the threat
and even the technology
to neutralize it
Boom!
That is just dangerous
Kapow!
But where some see danger,
others sense an opportunity
Asteroids contains
precious metals and water
Perhaps we can learn
to mine them for their wealth
There are millions and millions
of these objects
in the solar system,
and we've only just begun
to understand
their resource potential
Asteroids could be the biggest
threat humanity faces
or a great opportunity
"Asteroids: Doomsday or Payday?"
Right now on NOVA.
A rock tumbles through space:
material left over from when
the planets first formed
It has orbited the sun
for four-and-a-half
billion years
An asteroid
It's 30 meters,
or 90 feet, across,
half the size
of a small office building
Mass: 100,000 tons
It's on a collision course
with Earth
Ground-based telescopes spot it
just days before impact
In its sights: a large city
There's panic on the streets
Why didn't we see it sooner?
Perhaps then we could have
saved ourselves
Now it's too late
The asteroid strikes
It hits with the energy
of over 100 atom bombs
Everything from downtown to
the outer city limits and beyond
is completely obliterated
This nightmare scenario
is just fiction
We can only hope
it never happens
But asteroids
have struck Earth before
Wind back 65 million years
A rock approximately
ten kilometers wide
smashes into planet Earth
It helps wipe out the dinosaurs
and around 70% of species
on the planet
Our planet also bears the scars
from much smaller strikes
This one: 50,000 years ago
But the danger from asteroids
still hangs over us today
They can catch us
completely by surprise
Our challenge is to understand
these potentially
devastating objects
So what exactly is an asteroid?
Asteroids are rocks
left over from the birth
of the solar system
4 6 billion years ago
As Mars and Jupiter form,
they leave a ring of debris
between them:
the asteroid belt
Asteroids are rocks
that should form another planet,
but Jupiter's gravity
prevents them from coalescing
The asteroid belt ranges
from roughly 150 to nearly
500 million kilometers away
Out here, asteroids pose
no threat to Earth
There are millions of asteroids
and comets in the solar system
Fortunately for us, most of them
are on very stable orbits
They stay where they're
supposed to be
and they live their lives
and evolve through their part
of the solar system
without ever coming close
to the Earth
Today, we have the technology
to visit these remote objects
NASA's Dawn probe
approaches the Vesta,
the second-largest asteroid
in the solar system
It returns these detailed images
It's now en route
to an even larger body: Ceres
But not all asteroids stay
in the asteroid belt
A random collision,
a planet's gravity,
even heat from the sun
can knock them into a different
orbit closer to Earth
Many of these
near-Earth asteroids
cross our path time and again
If they enter our atmosphere,
they become potentially
deadly meteors
Any fragments
that reach the ground,
we call meteorites
With the experience
of three missions
and over 200 days in space,
former Astronaut Ed Lu believes
it's only a matter of time
before one strikes us again
It's like cosmic roulette
The entire city of Las Vegas
was built upon the concept
that the house always wins
And in this game,
we're not the house
Our asteroid knowledge
and detection technologies
have improved rapidly
in recent decades
Many now believe asteroids
are a problem we can solve
Asteroid impacts are actually
the first natural disaster
that humans have a hope
of really preventing
We can maybe try and model
where earthquakes happen,
we can try to predict how
frequently tornadoes happen
We can't stop them
from happening
Asteroid impacts,
we might actually be able
to do something about that
in the very near future
So how can we overcome
the asteroid threat?
Observations have revealed
almost 1,000 asteroids
larger than a kilometer
in near-Earth orbits
These are potentially
large enough
to cause a global catastrophe
But we know where
most of them are
The chances of a strike
are vanishingly small
The immediate danger
comes from smaller asteroids,
less than one kilometer,
or about 3,000 feet, across
There are millions of these
in orbits that pass near Earth
We've discovered roughly
10,000 near-Earth objects
that can get fairly close
to the Earth
To put that in perspective,
only about 20 years ago,
we had less than 100
For every near-Earth asteroid
we have detected,
there are thousands
that we haven't
Ed Lu believes we need to locate
and track them
50 years ago, 100 years ago,
if we were wiped out
by an asteroid,
that was just bad luck
Today, if we are hit
by a major asteroid,
that is not bad luck anymore
That is negligence
We have the technology
to detect asteroids
long before they hit us
We've found many
of the big ones,
but smaller rocks could hit
at any time
The Minor Planet Center
at the Smithsonian
Astrophysical Observatory
is at the center of the mission
to track every asteroid
in the solar system
Gareth Williams is tasked
with deciding
which asteroids are a cause
for concern
The computers in this room
are really the nerve center
of the Minor Planet Center
The 103 million observations
and 600,000 orbits
that are stored
on the computers here
are the primary source
of information for the world
on the motions of minor bodies
in the solar system
Around 450 observer stations
feed information
to the Minor Planet Center
But most near-Earth
asteroid discoveries
come mainly from professional
optical telescopes
To date, we have found most of
the large main belt asteroids
Where we are lacking
in knowledge
are the smaller
near-Earth objects
Anything about
50 meters diameter,
we are very incomplete in our
knowledge of those objects
Every single asteroid the Minor
Planet Center knows about
was discovered using
the same basic principle
Optical telescopes capture
several images of the night sky
minutes, hours or days apart
Astronomers use computers
to compare the images
The stars stay still
Asteroids move
Once the computers identify
a new near-Earth asteroid,
further observations
are requested
The asteroid must be tracked
to decide if it's a threat
We can get an orbit from
three nights of observation
To get a good orbit,
we generally require
observations over an arc
of a month
The primary reason
we track asteroids
is to have some idea
of if and when an object
is going to approach the Earth
very closely or hit the Earth
To complete his risk assessment,
Gareth can request the help
of a different kind of telescope
to track the asteroid's orbit
This is NASA's
Goldstone Observatory
in the Mojave Desert
Standard optical telescopes
use reflective mirrors
to watch a patch of sky
Goldstone is different
It uses radar to zoom in on
and track an asteroid
This is a DSS-14,
a 70-meter radio telescope
It has a high-powered
radar transmitter on it
that we use for tracking
and imaging near-Earth asteroids
when they're close to the Earth
The Goldstone telescope
acts like a giant flashlight,
but instead of light,
it sends out a focused beam
of electromagnetic radio waves
toward the asteroid
By timing how long it takes
the radio waves
to hit the asteroid
and bounce back,
astronomers can verify
exactly where it is in space
And once locked onto it,
they can watch how it moves
over time
Radar is a very useful
instrument
in preventing newly discovered
asteroids from being lost
Usually, their orbits
are not well determined,
so if you get the radar
measurements,
you manage to extend
how far in future you know
where these objects are
This automatically provides you
with an early warning system
You know if there is
any chance of impact
many decades, maybe even
centuries in the future
The data Goldstone produces
is so precise,
it can predict an asteroid's
path years in advance
February 15, 2013:
Asteroid DA14 comes within
just 28,000 kilometers of Earth,
inside the orbit
of many satellites
But NASA and other telescopes
around the world
have already tracked
the asteroid for a year
They know its path
with great precision
They're 100% certain
that we're safe
The asteroid passes at exactly
the distance they predict
It was less than one-tenth
of the distance
between the Earth and the moon
In advance of the fly-by,
we expected that it would be
roughly 50 meters in diameter,
and this was the closest
approach by something that size
that we've ever known about
in advance
But our detection systems
don't always work this well
That becomes painfully clear
on the exact same day
that the world's telescopes
track DA14 passing by
Another asteroid approaches:
one our telescopes
fail to detect
It hits us
9:20 a m, Siberia, Russia
A fireball rips through the sky
over the city of Chelyabinsk
Smartphones and car dash cameras
provide an unprecedented view
A shockwave crashes down
on the city
Windows blow in
Doors are flattened
More than 1,000 are injured
The Chelyabinsk asteroid impact
was a game-changer
in the sense that
it makes it real for people
And that's important because
human psychology is such that
if something hasn't happened
in my lifetime,
I tend to discount it
NASA asks astrophysicist
Peter Brown
for an early estimate
of the size of the blast
He uses a highly sensitive
global system
of above-ground microphones
designed to detect
illegal nuclear bomb blasts
The system is part of the
nuclear weapons test ban treaty
We're listening to the very
lowest, very deep bass tones
reflecting the huge amount
of energy in this explosion
As the explosions get bigger,
the tone of the shockwave
or the tone of the sound
gets lower and lower and lower
until it's below the level that
human hearing is able to detect
Peter is shocked
by what he discovers
In this particular case,
the signal was very obvious
It was huge,
and the most startling
characteristic
was the fact that it was a very,
very low tonal frequency,
much lower than anything
I'd ever seen before
His official estimate
of the explosion's power
is nearly 500 kilotons...
More powerful than the blast
from a large nuclear bomb
from the American arsenal
The atomic bomb
dropped on Hiroshima
was about 15 to 20 kilotons,
so 15,000 to 20,000 tons of TNT
So this event, Chelyabinsk, is
about 20 to 30 times that event,
which is what makes it so
unusual but also so destructive
The event is huge
So why didn't we see it coming?
Physicist Mark Boslough
is one of the first scientists
to visit Chelyabinsk
after the meteor strike
He's convinced the answer
is tied up
with the asteroid's trajectory...
The direction it came from
He believes
he can calculate this
with the help
of amateur video footage
Using several key images,
he returns to the precise
locations where they were shot
He has to do this at night
when the stars are out
Well, I am doing
a stellar calibration
So we got
One of our videos
was from a dash cam,
from a car parked
in this parking lot,
and the fireball streaked
across the sky here
We're looking south,
it went from left to right
And what we really want to do
is determine the exact angles
to the fireball
as seen from this location
Mark's goal is to plot the exact
trajectory of the meteor
from where it appears in the sky
Standing where the eye-witness
video was originally taken,
Mark records its GPS coordinates
He then takes a picture of the
night sky with his own camera
He'll use the stars in his photo
to help him pinpoint
the meteor's path in the video
So if the stars show up
on the digital camera,
we can get those angles
and then calibrate that image
that was taken from the dash cam
and know exactly the angles
to the trajectory
of the fireball
By lining up his star field
photo against the video frame,
Mark can get a fix
on where the fireball appeared
relative to the stars
He repeats this process
at several locations
Finally, Mark uses
simple geometry
to locate the fireball
in three-dimensional space,
building a model
that shows exactly the angle
and direction of its approach
Mark's calculations explain
why our telescopes
fail to see
the Chelyabinsk meteor coming:
it approaches from the direction
of the sun
It's masked by the sun's glare
And the Chelyabinsk meteor
is not unusual
Any near-Earth asteroid
is completely invisible
at the point when its orbit
passes between the Earth
and the sun
That's a big gap
in our detection capability
And that's the issue right now
Our current surveys,
the current things
that we're doing right now
to find asteroids
are totally inadequate
We need to bump this up
by about a factor of 100
So we have a problem
Ground-based telescopes
can only detect asteroids
by looking away from the sun
into the night sky
But half the asteroids
that hit us
come from the other direction
There could now be a solution:
putting a telescope into space
Currently, all of the near-Earth
object discoveries
are made with ground-based
optical telescopes
If we could get
above the earth's atmosphere,
we could do a far more
efficient survey
NASA has already demonstrated
the capabilities
of space telescopes
to identify near-Earth objects
In 2010, the WISE mission
detects 135 near-Earth asteroids
before the telescope is retired
The problem is
there may be millions more
Many believe we now need
a longer-term mission
designed for asteroid detection
But the funds
haven't been allocated
Though NASA is rebooting
WISE as an asteroid-hunter,
a tailor-made asteroid
detection system from NASA
looks a long way off
So the private sector
is stepping in
B612, a non-profit foundation,
is financing a new infrared
space telescope
based on existing designs
like this one
Its sole aim: finding more
near-Earth asteroids
Former astronauts Ed Lu
and Rusty Schweikart
are leading the $400 million
fundraising drive
This is a public service
We're a non-profit corporation
We're not doing this
to make money
We're doing this, you know,
to help extend the domain
of life on Earth here
Codenamed Sentinel,
the telescope will orbit the sun
just like Earth
and the other planets
But with a similar orbit
to Venus,
it can look out towards Earth's
path with the sun behind it
Looking away from the sun
will enable it
to detect asteroids
we cannot see from Earth
Sentinel is an infrared
space telescope
that the B612 Foundation
is building,
and we're going to launch it
in 2018
As it moves around
the solar system,
it will scan Earth's orbit,
and we'll discover
just in its first year
200,000 near-Earth objects
Again, compare that
to our current discovery rate
of about a thousand
Sentinel will help
detect asteroids
between Earth and the sun
It will make it easier to find
that potentially dangerous group
of near-Earth asteroids:
not just those
over 140 meters wide,
but also millions
of smaller objects
Historically, these have been
hard to detect
Sentinel's technology
could change that
Sentinel will be built here
by Ball Aerospace,
who also helped design
and produce
the Spitzer and Kepler
Space Telescopes
Program Manager John Troeltzsch
is planning to use their proven
technology in the new telescope
So Sentinel has come in
at the right point in time
We've developed
a lot of technologies
over the last 20 years
in detectors,
in telecommunications systems,
in spacecraft, in solar power
All these things
are coming together today
to help produce
the Sentinel spacecraft
Sentinel's most important
technology
will be its infrared detector
This will find
the smaller asteroids
that most worry scientists
by searching for the heat
they emit
Asteroids are very hard to see
against the dark background
in deep space
Here's a piece of a meteorite
Same composition as an asteroid,
really hard to see
in visible light
However, when I take
my infrared camera,
wow, it shows right up
And I can see it clearly
against the background
This is the advantage
that Sentinel has
for infrared detection
of asteroids
Sentinel's infrared capability
is essential
for detecting small asteroids
Asteroids around a kilometer
across are easier to spot
Even though they're dark,
their size means
they reflect enough sunlight
for us to see them
Smaller dark asteroids
reflect less light,
but infrared detectors
will pick up the heat they emit
That gives Sentinel
a huge advantage
Our design for Sentinel
is designed to find 90%
of 140 meter or larger asteroids
that might threaten the Earth,
the things that can
really destroy
large areas of a continent,
really do major damage
The goal is to launch
Sentinel in 2018
Meanwhile, NASA is helping fund
a ground-based system
to complement existing
telescopes in Hawaii
Codenamed ATLAS, it will provide
a few weeks' warning,
enough for at least some people
to evacuate
Even this won't find every
asteroid that threatens us
Earth is still flying blind
through a solar system
full of undetected asteroids
The nightmare scenario
is still entirely possible
A small asteroid undetected
by our current technologies
could strike at any time
And we now know that the threat
is not just from rocks
140 meters across
Even far smaller asteroid
strikes can be devastating
When scientists use data
from the Chelyabinsk blast
to calculate
the asteroid's size,
they discover it's tiny:
20 meters across,
an asteroid so small,
no one thought
it could cause a problem
In fact, rocks this small
can do far more damage
than we saw at Chelyabinsk
It all depends on four factors:
the asteroid's composition,
its speed, angle of attack,
and where it strikes
In the immediate aftermath
of the Chelyabinsk strike
in Siberia,
physicist Mark Boslough
continues his research
He hunts through the snow
to find meteorites:
fragments of the asteroid
What's amazing to me, though,
when you think about it,
I mean, this is part
of an asteroid
that had been, you know,
floating through space,
orbiting the sun
for billions of years
And two weeks ago,
it exploded in the atmosphere,
dropped to the ground,
and here I am,
holding it in my hand
That's amazing
Mark takes the fragment
to a lab in Yekaterinburg
and studies it
under an electron microscope
There's a crack here
A crack?
Yes
What's the scale on that?
About three microns
Mark's analysis reveals that
the fragment is mostly rock,
and it's shot through
with cracks
These are scars from previous
collisions in space
When it smashed
into our atmosphere
at 40,000 miles per hour,
and reaching more than
3,600 degrees Fahrenheit,
the cracks help break
the meteor apart
The way we understand it is
it hits the atmosphere
going so fast
that there's
so much stress on it
that it actually breaks
the asteroid
It exceeds the strength
of the asteroid,
and that can happen very,
very fast
The Chelyabinsk meteor
disintegrates
15 miles above the ground
It releases a shockwave
with the energy
of almost 30 atom bombs
It's this shockwave
that does the damage
The Chelyabinsk meteor explodes
because it's made
of fractured rock
But not all asteroids
are made this way
Some are made of metal
The Natural History Museum
in London
holds one of the world's largest
collections of meteorites
Caroline Smith studies them,
and it's clear to her that
not all meteorites are alike
Meteorites come in three
different flavors:
stones, stony irons, or irons
These two that I have here,
these are called
stony iron meteorites,
and these are a mixture
of rock and metal
Because they've got
so much metal in them,
they are much heavier than
a normal rock from Earth
I mean, that's a good
sort of 12, 15 kilograms
And this is an iron nickel
meteorite, and it's heavy
This is about
three times as heavy
as the one that
I've just shown you
It does put into context the
type of damage that you can get
from something of that size
Metallic asteroids are denser
and tougher than rocky ones,
so a metallic asteroid the size
of the Chelyabinsk rock
could punch through
the atmosphere
instead of breaking up,
hitting Earth's surface
more or less intact
And here's the proof:
Meteor Crater, Arizona
Over one kilometer across
and more than 150 meters deep,
yet the meteor that creates it
50,000 years ago
is only one-and-a-half times the
size of the Chelyabinsk meteor
The difference is that
it's metallic
It smashes into the ground with
the power of 500 atom bombs
An iron meteorite
slammed into the rock here
with most of its cosmic speed
still intact
at about 40,000 miles per hour
The energy released
in that impact
was something on the order
of ten megatons
of TNT equivalent,
and it's that energy
that was responsible
for excavating this
enormous hole in the ground
and spewing that rock
into the desert around us
Composition makes
a big difference
to the destructive power
of an asteroid
Metallic asteroids
stand the best chance
of surviving
the brutal atmosphere
But even stony asteroids
can still be devastating
Russia, 1908:
a meteor explodes in the sky
above Tunguska, Siberia
Calculations show
that the asteroid
is just twice the width
of the Chelyabinsk rock
But where the Chelyabinsk blast
knocks out windows,
the Tunguska strike flattens
hundreds of square miles
of forest
Its effects are similar
to this nuclear test blast
captured on film
Even 20 years later,
when these images were taken,
the effects are still evident
So why the difference
between the two meteors?
Video images show
the Chelyabinsk asteroid
approaches at a particularly
shallow angle
Mark Boslough feeds that
information into a computer
used to model the behavior
of nuclear weapons
This simulation shows
the effects
of the meteor's trajectory
on its destructive impact
And you get this enormous
fireball,
and that fireball continues
to move downward
and it pushes a shockwave
ahead of it
So these are like
mushroom clouds
with two big, giant nuclear
explosions at the bottom
The shock from the explosion
continues to push forward
and it starts to move downwards
You can see that it's descending
It's down to about
ten kilometers
above the surface here,
at ground zero
The simulation shows that
because the meteor enters
at a shallow angle,
much of the energy
is lost horizontally
The shockwave is destructive,
but it would have been far worse
if had been focused
more downward
and the explosion
had been closer to the ground
This is what Mark believes
happens in Tunguska in 1908
The Tunguska explosion
was much closer to the ground
and it was much more intense
in terms of energy release,
and therefore the blast wave
was much stronger,
and that's why
it blew down trees
over this wide area
almost a thousand square miles
No one dies
in the Tunguska blast,
but only because
no one lives here
Someday, a similar strike
could happen over a city
It could kill millions
I've seen maps
of the Tunguska blast area
overlaid with a map
of Washington, D C,
and it extends beyond
the Beltway in every direction
An asteroid has more damage
potential on the ground
than a nuclear bomb
of the same energy
Fortunately, most asteroids
are relatively small
and strikes are rare
Better detection will help,
but detection alone
is not enough
If we find an asteroid
heading toward Earth,
what can we do about it?
Sci-fi movies
always have the answers
The hero flies up
and blows the asteroid apart
So this is the real
Hollywood way
of looking at an asteroid's
impact hazard mitigation
So they detect,
with just enough time,
that there's this giant asteroid
or comet or something
coming in towards the Earth,
and everyone decides,
"A-ha, well, we're gonna blow it
to kingdom come
We'll just nuke it"
Blowing an asteroid apart
sounds extreme,
but right now, scientists
are exploring ways
to harness technology
to save us from the next
big asteroid strike
We need to think about, "What is
the response of the object?"
"Are we going to fragment it?
"Is that okay?
"Are the fragments
going to recombine
"or fly off out of the way,
"or are fragments
going to hit the Earth
that we need to worry about?"
To learn how these fragments
might behave,
we can simulate a similar impact
here on Earth
And Peter Schultz is the man
who pulls the trigger
He operates one of the few guns
in the world
fast enough to model
an asteroid strike
This hydrogen-powered gun
is targeted into a reinforced
metal safety chamber
Inside this chamber is a small
resin replica of an asteroid
It's there to illustrate
two different approaches
to keeping Earth safe:
destruction and deflection
So today, we're going to do
two experiments
The first one will actually
destroy the asteroid
by using this projectile,
about a quarter inch across
And the second one,
we'll use this projectile:
it's about an eighth inch across
This will not destroy
the asteroid
but instead will form a crater,
and that's really intended
just to deflect it
without destroying it
The aluminum pellets
will hit the asteroid replica
at almost 12,000 miles per hour
That's over three miles
per second
High-speed cameras are needed
to record every millisecond
of the impact
Even this small simulation
will be violent
The team keeps a safe distance
in the control room
High voltage is good
We have ready lights
Oh, jeez!
We really busted the devil
out of this
The high-speed video
allows Peter to analyze
the impact of the larger
projectile in minute detail
Here's the projectile coming in,
you can actually see it
coming in
It's going to hit right there
Boom!
That is just dangerous
Kapow!
There's nothing left except for
something right in the center
The last piece, that core
still could be a threat,
but it's a lot smaller
We're way down
in terms of a threat
So this is one option we got:
we blow the whole thing
to smithereens
But we always have to wonder,
"Is there something left over?"
Scale this up
to blowing apart a real asteroid
and the problem is clear:
deadly fragments of rock
could still rain down on Earth
So the possible problems
with destroying an object,
or disrupting it, we say,
is that you need to have
enough time for the fragments
that are then flying off
in all kinds of directions
to get out of the way before
the Earth passes through there
Blowing an asteroid apart
could make the problem worse
instead of solving it
Luckily, there is another option
Rather than blast
the asteroid apart,
we could use an impact
to change its course
For a lot of objects, you don't
actually need to blow them up
to prevent them from hitting
Earth and making a crater
For me, the most realistic
are what we call
kinetic impactors
for small asteroids,
and that's basically
a cannonball
shot from a spacecraft
to knock it off course
That might reduce
the fragment problem,
but it still needs to be tested
Peter sets up the gun
with a smaller projectile
This shot should create
a crater, but not an explosion
Here we go
Okay, so let's see what we have
Whoa!
Oh, look at that!
This time, the asteroid
stays mostly intact
And this is the crater forming
So what's going to be
interesting is to see,
"Does it make it move?"
Boom!
Then we see that jet come out...
That's really hot gas,
it's a plasma...
And we can see
the ejecta forming,
and now it begins to move
The collision creates a blast
of super-heated impact material
spraying out from the simulated
asteroid
It acts like a rocket
firing out into space
The asteroid is nudged
off course
So the impact hit it,
its momentum
is now shoving this,
and with enough time,
maybe this would get it
out of our way
So I think we're illustrating
that we don't have to destroy
the whole thing to make it move;
we just have to have
enough energy and momentum
to give it a nudge
Could our planet and our lives
be saved by a mere nudge?
The reason it's so easy
is because the Earth's
a moving target
The Earth's about
8,000 miles across,
and it's moving
65,000 miles an hour
So every eight minutes,
the Earth moves a distance
equal to its size
So all I'm really going to do is
upset the timing a little bit
If I make the asteroid show up
at the collision point
three minutes early
or three minutes late,
the Earth's gone,
and that's all it takes,
that's why it's so easy
at large distances
But this would be
a gradual process
The projectile
will have to be launched
many years before the asteroid
comes close to Earth
This is an urgent problem
because if there is
an asteroid out there
that is already on a trajectory
to hit the Earth
and we're not finding out
about it today,
then we're losing
valuable time it takes
to deflect that asteroid,
because what you really need
is time
You need a decade of warning,
and then it's actually
easy to do
But you need time
So there are two clear options
to prevent asteroid strikes:
Blast the asteroid apart
or deflect it
And there is another way
You could do something called
a gravity tractor,
which is something invented
by myself
and an astronaut named Stan Love
And you just hover
a small spacecraft near it
and you tow it
Even an object
as small as a space probe
has its own gravity
It's incredibly weak,
but over time,
it acts like a tow rope,
altering the asteroid's course
Now, it's not as effective
as a kinetic impactor,
but it's controllable
The purpose
of the gravity tractor
is really to fine tune
the deflection
So it appears that we have
the technical capability
to deflect an asteroid
But it will take
a major investment
to prevent the nightmare
scenario:
a small asteroid
we cannot detect
obliterating a major city
And now there's a new question:
could that same technology
be applied
to turn asteroids
from threat to opportunity?
To answer that question,
consider the birth of our planet
I think it's a fairly
widely-held consensus view
that asteroids' initial impacts
with the Earth
four-and-a-half
billion years ago
seeded the Earth
with a veneer of water
and carbon-based materials
that allowed life to form
These are the building blocks
of life
Asteroids probably dumped
organic compounds
onto the early Earth,
and alongside those
may have come
other beneficial materials:
platinum, gold and water,
all valuable resources on Earth
Could asteroids be a new source
of these materials in space?
Chris Lewicki is president
and chief engineer
of Planetary Resources,
a company that hopes to mine
asteroids for profit
We are mining asteroids today
Some of the most productive
metal mines on Earth
are the site of asteroid impacts
hundreds of millions
of years ago
So to go to space,
in some cases, to the source,
we can get these materials
in much more abundance
than they exist naturally
in the Earth's crust
A single asteroid
of between 200 and 500 meters
could contain as much platinum
as we have mined
in the whole of human history
But Planetary Resources
and other companies
are most interested
in another resource:
water locked up
in the asteroid's rock
I think water is the most
important resource
in developing space
because it enables everything
that follows,
and by taking the water
and breaking it
into hydrogen and oxygen,
we can create rocket fuel,
the same rocket fuel that we use
to launch space shuttles
and to explore space
According to Dale Boucher, CEO
of another space mining company,
producing rocket fuel from water
is simple
So now we're making rocket fuel
This is just water in here,
and we've got
a very simple process
run by a couple
of little batteries
passing electric current
through here
We're going to separate
this water into hydrogen,
hydrogen bubbling off this side
And on this side is oxygen
As you can see, there's twice
as much hydrogen as oxygen
because the formula is H20
Many rockets use liquid hydrogen
and oxygen as fuel
Mix them together
and add a spark,
and you get explosive thrust
Okay, so we're going to capture
the hydrogen in this tube,
we're going to bleed
this valve off
All of the hydrogen
that was bubbled off
is coming up in here
Because it's lighter than air,
it will float up
And what we're gonna do
is tilt it like this
and strike a match
We have lift off!
The weight of a rocket
at lift-off is almost all fuel
It burns almost all that fuel
just getting into orbit
If fuel could be produced
from asteroid water,
rockets could maneuver more
easily and even travel faster
This is something
that is abundant in space
On a single 75-meter asteroid,
we have enough water
to have fueled the entire
US space shuttle program
So how would the ability
to refuel in space
affect the future exploration
of our solar system?
In my mind, it makes sense
to go to an asteroid,
mine water, produce rocket fuel
and hold it there
in an orbital station,
let's say,
so that ships or equipment
or robotic missions can stop in,
have a sandwich, have a coffee,
refuel the rocket ship
and go on to Mars
Imagine driving
your car somewhere
without the opportunity
to stop by and gas it up
This is what we've been doing
in exploring space to date
We now have the potential
of being able to refuel
a spaceship on its way
not only from Earth
into outer space
but to refuel
for farther destinations
in the solar system
The rocket fuel is out there
The challenge is to find
the right asteroids,
get to them,
and then extract the water
All of this demands
new technology,
and several companies are
working on that right now
Planetary Resources plan to use
a newly designed telescope
called Arkyd
to find suitable asteroids
Mining in space starts
much the same as mining does
here on Earth
We start with prospecting
and identifying the resource
And we will survey
maybe dozens of asteroids
until we find the one
that has the most interesting
and most economically viable
combination of features
Assuming they find
an asteroid to mine,
the next challenge is
to reach it
Here, the technology for this
is still on the drawing board
NASA is studying ways
to grab an asteroid
and tow it nearer to Earth
This is a very ambitious
engineering project
So the idea is
to send a spacecraft
out to a near-Earth asteroid...
Not to the asteroid belt
outside of Mars,
but to one that actually
on its own comes near Earth
and is small enough...
And then take the asteroid
with a Kevlar bag
And the asteroid, of course,
is spinning relative
to the spacecraft,
and so it would tangle itself up
in the Kevlar,
which would slow it down
and give the spacecraft
something to hold on to
They would then haul it back
and put it into orbit
around the moon
and have someplace
for scientists to go
to look at this large piece
of space rock still in space
For now, it's unclear whether
this program will go forward
But even if the right asteroid
can be found and captured,
the next challenge will be
extracting the resources
Mining expert Dale Boucher
believes there are lessons
from mining on Earth
that will help with the much
tougher task of mining in space
Terrestrial mining is a brute
force type of activity
You know, when we're drilling,
we've got huge 100-pound drills
driving into the rock
with massive air pressure
behind it, trying to excavate
The excavator itself is massive,
weighs many tons
It's using that dead weight
to its advantage
That's what it needs
to get the traction
to push its bucket
into that rock
and pull that rock out of there
None of this will work in space
There's very little gravity,
and the rocks can be cold:
hundreds of degrees below zero
Mining in space demands
whole new technologies
The big difference is gravity,
which means that
we have more problems
with trying to push enough force
on a drill bit, let's say,
or on an excavator bucket
to try and make that
do our work for us
So we have to start thinking
about how we anchor ourselves
to these very virtually
weightless bodies
Dale has been involved
in developing
specialized mining
and drilling technology
to meet these
extraterrestrial challenges
This drill bit
has been designed for use
in the lower temperatures
of the moon
The same technology
might possibly be adapted
for mining asteroids
So this drill is trying to drill
through this simulated
lunar material
that's got water in it,
and we've cooled it down
to liquid nitrogen temperatures
to simulate the temperature
on the surface of the moon,
near the south pole,
where this drill
is supposed to end up
This is different
from the mining drills
used here on Earth
To save energy and weight,
it uses less power
and is much slower
So the drill runs on
about less than
100 watts of power
It takes a very long time
to drill:
it's like watching paint dry
To do a full meter sample
would take about an hour
to an hour-and-a-half,
depending on how hard
the material actually is
Even if the technology
is within reach,
it would be extremely costly
to find suitable asteroids,
relocate them
and extract their resources
Is there a big enough payoff?
If we're going to exploit
asteroids,
I think we need to really do
a cost benefit
It's expensive to get up there
It's plausible
We can do this... after all,
we've been to the moon...
But I think this requires
some very serious study
We know it's possible
to reach an asteroid
and bring samples to Earth
because the Japanese Hayabusa
probe has already done it
But the samples it brought back
in 2010 were microscopic
To mine significant quantities
is an entirely different
challenge
So is the idea of mining
asteroids premature?
Some believe there's no point
in trying to exploit asteroids
until we are safe from them
Well, I can tell you that
you can't mine an asteroid
if you don't know where it is
in the same way you can't
deflect an asteroid
or protect the Earth
from an asteroid
if you don't know where it is
So the first step to all of this
is building Sentinel,
because Sentinel will find the
asteroids in our solar system
We can deal with the threat
of asteroids
and the opportunity that
they present simultaneously
As we develop the technology
to detect, characterize
and ultimately mine asteroids,
it's that very same technology
that will allow us to identify
potentially hazardous asteroids
and take action
This will drive expansion and
exploration of the solar system,
enabling humanity to eventually
live and work and play
in space permanently
A paradox
Are asteroids the biggest threat
humanity faces
or a new opportunity?
As our knowledge
and technology improve,
could it be that they are both?
Captioned by
Media Access Group at WGBH
access wgbh org
Our solar system
is full of deadly missiles
that could strike at any time
It's like cosmic roulette
You can't go on
playing a game of chance
and expect to keep winning
Killer asteroids
Trillions of tons of rock,
hurtling through space at tens
of thousands of miles per hour
Some are on a collision course
with earth
An asteroid has
more damage potential
than a nuclear bomb
of the same energy
65 million years ago,
a huge asteroid wipes out
much of life on Earth
But strikes aren't all
ancient history
In 2013, a much smaller asteroid
terrorizes this Siberian city
For many, this really was
a wake-up event
Now the race is on
to understand the danger
We know they're out there
When and where
will the next one strike?
Will it hit on a city?
I don't know
The point is
we have to find that out
We really need to upgrade
the search capability
We stand at a crossroads
Only now do we have the ability
to identify the threat
and even the technology
to neutralize it
Boom!
That is just dangerous
Kapow!
But where some see danger,
others sense an opportunity
Asteroids contains
precious metals and water
Perhaps we can learn
to mine them for their wealth
There are millions and millions
of these objects
in the solar system,
and we've only just begun
to understand
their resource potential
Asteroids could be the biggest
threat humanity faces
or a great opportunity
"Asteroids: Doomsday or Payday?"
Right now on NOVA.
A rock tumbles through space:
material left over from when
the planets first formed
It has orbited the sun
for four-and-a-half
billion years
An asteroid
It's 30 meters,
or 90 feet, across,
half the size
of a small office building
Mass: 100,000 tons
It's on a collision course
with Earth
Ground-based telescopes spot it
just days before impact
In its sights: a large city
There's panic on the streets
Why didn't we see it sooner?
Perhaps then we could have
saved ourselves
Now it's too late
The asteroid strikes
It hits with the energy
of over 100 atom bombs
Everything from downtown to
the outer city limits and beyond
is completely obliterated
This nightmare scenario
is just fiction
We can only hope
it never happens
But asteroids
have struck Earth before
Wind back 65 million years
A rock approximately
ten kilometers wide
smashes into planet Earth
It helps wipe out the dinosaurs
and around 70% of species
on the planet
Our planet also bears the scars
from much smaller strikes
This one: 50,000 years ago
But the danger from asteroids
still hangs over us today
They can catch us
completely by surprise
Our challenge is to understand
these potentially
devastating objects
So what exactly is an asteroid?
Asteroids are rocks
left over from the birth
of the solar system
4 6 billion years ago
As Mars and Jupiter form,
they leave a ring of debris
between them:
the asteroid belt
Asteroids are rocks
that should form another planet,
but Jupiter's gravity
prevents them from coalescing
The asteroid belt ranges
from roughly 150 to nearly
500 million kilometers away
Out here, asteroids pose
no threat to Earth
There are millions of asteroids
and comets in the solar system
Fortunately for us, most of them
are on very stable orbits
They stay where they're
supposed to be
and they live their lives
and evolve through their part
of the solar system
without ever coming close
to the Earth
Today, we have the technology
to visit these remote objects
NASA's Dawn probe
approaches the Vesta,
the second-largest asteroid
in the solar system
It returns these detailed images
It's now en route
to an even larger body: Ceres
But not all asteroids stay
in the asteroid belt
A random collision,
a planet's gravity,
even heat from the sun
can knock them into a different
orbit closer to Earth
Many of these
near-Earth asteroids
cross our path time and again
If they enter our atmosphere,
they become potentially
deadly meteors
Any fragments
that reach the ground,
we call meteorites
With the experience
of three missions
and over 200 days in space,
former Astronaut Ed Lu believes
it's only a matter of time
before one strikes us again
It's like cosmic roulette
The entire city of Las Vegas
was built upon the concept
that the house always wins
And in this game,
we're not the house
Our asteroid knowledge
and detection technologies
have improved rapidly
in recent decades
Many now believe asteroids
are a problem we can solve
Asteroid impacts are actually
the first natural disaster
that humans have a hope
of really preventing
We can maybe try and model
where earthquakes happen,
we can try to predict how
frequently tornadoes happen
We can't stop them
from happening
Asteroid impacts,
we might actually be able
to do something about that
in the very near future
So how can we overcome
the asteroid threat?
Observations have revealed
almost 1,000 asteroids
larger than a kilometer
in near-Earth orbits
These are potentially
large enough
to cause a global catastrophe
But we know where
most of them are
The chances of a strike
are vanishingly small
The immediate danger
comes from smaller asteroids,
less than one kilometer,
or about 3,000 feet, across
There are millions of these
in orbits that pass near Earth
We've discovered roughly
10,000 near-Earth objects
that can get fairly close
to the Earth
To put that in perspective,
only about 20 years ago,
we had less than 100
For every near-Earth asteroid
we have detected,
there are thousands
that we haven't
Ed Lu believes we need to locate
and track them
50 years ago, 100 years ago,
if we were wiped out
by an asteroid,
that was just bad luck
Today, if we are hit
by a major asteroid,
that is not bad luck anymore
That is negligence
We have the technology
to detect asteroids
long before they hit us
We've found many
of the big ones,
but smaller rocks could hit
at any time
The Minor Planet Center
at the Smithsonian
Astrophysical Observatory
is at the center of the mission
to track every asteroid
in the solar system
Gareth Williams is tasked
with deciding
which asteroids are a cause
for concern
The computers in this room
are really the nerve center
of the Minor Planet Center
The 103 million observations
and 600,000 orbits
that are stored
on the computers here
are the primary source
of information for the world
on the motions of minor bodies
in the solar system
Around 450 observer stations
feed information
to the Minor Planet Center
But most near-Earth
asteroid discoveries
come mainly from professional
optical telescopes
To date, we have found most of
the large main belt asteroids
Where we are lacking
in knowledge
are the smaller
near-Earth objects
Anything about
50 meters diameter,
we are very incomplete in our
knowledge of those objects
Every single asteroid the Minor
Planet Center knows about
was discovered using
the same basic principle
Optical telescopes capture
several images of the night sky
minutes, hours or days apart
Astronomers use computers
to compare the images
The stars stay still
Asteroids move
Once the computers identify
a new near-Earth asteroid,
further observations
are requested
The asteroid must be tracked
to decide if it's a threat
We can get an orbit from
three nights of observation
To get a good orbit,
we generally require
observations over an arc
of a month
The primary reason
we track asteroids
is to have some idea
of if and when an object
is going to approach the Earth
very closely or hit the Earth
To complete his risk assessment,
Gareth can request the help
of a different kind of telescope
to track the asteroid's orbit
This is NASA's
Goldstone Observatory
in the Mojave Desert
Standard optical telescopes
use reflective mirrors
to watch a patch of sky
Goldstone is different
It uses radar to zoom in on
and track an asteroid
This is a DSS-14,
a 70-meter radio telescope
It has a high-powered
radar transmitter on it
that we use for tracking
and imaging near-Earth asteroids
when they're close to the Earth
The Goldstone telescope
acts like a giant flashlight,
but instead of light,
it sends out a focused beam
of electromagnetic radio waves
toward the asteroid
By timing how long it takes
the radio waves
to hit the asteroid
and bounce back,
astronomers can verify
exactly where it is in space
And once locked onto it,
they can watch how it moves
over time
Radar is a very useful
instrument
in preventing newly discovered
asteroids from being lost
Usually, their orbits
are not well determined,
so if you get the radar
measurements,
you manage to extend
how far in future you know
where these objects are
This automatically provides you
with an early warning system
You know if there is
any chance of impact
many decades, maybe even
centuries in the future
The data Goldstone produces
is so precise,
it can predict an asteroid's
path years in advance
February 15, 2013:
Asteroid DA14 comes within
just 28,000 kilometers of Earth,
inside the orbit
of many satellites
But NASA and other telescopes
around the world
have already tracked
the asteroid for a year
They know its path
with great precision
They're 100% certain
that we're safe
The asteroid passes at exactly
the distance they predict
It was less than one-tenth
of the distance
between the Earth and the moon
In advance of the fly-by,
we expected that it would be
roughly 50 meters in diameter,
and this was the closest
approach by something that size
that we've ever known about
in advance
But our detection systems
don't always work this well
That becomes painfully clear
on the exact same day
that the world's telescopes
track DA14 passing by
Another asteroid approaches:
one our telescopes
fail to detect
It hits us
9:20 a m, Siberia, Russia
A fireball rips through the sky
over the city of Chelyabinsk
Smartphones and car dash cameras
provide an unprecedented view
A shockwave crashes down
on the city
Windows blow in
Doors are flattened
More than 1,000 are injured
The Chelyabinsk asteroid impact
was a game-changer
in the sense that
it makes it real for people
And that's important because
human psychology is such that
if something hasn't happened
in my lifetime,
I tend to discount it
NASA asks astrophysicist
Peter Brown
for an early estimate
of the size of the blast
He uses a highly sensitive
global system
of above-ground microphones
designed to detect
illegal nuclear bomb blasts
The system is part of the
nuclear weapons test ban treaty
We're listening to the very
lowest, very deep bass tones
reflecting the huge amount
of energy in this explosion
As the explosions get bigger,
the tone of the shockwave
or the tone of the sound
gets lower and lower and lower
until it's below the level that
human hearing is able to detect
Peter is shocked
by what he discovers
In this particular case,
the signal was very obvious
It was huge,
and the most startling
characteristic
was the fact that it was a very,
very low tonal frequency,
much lower than anything
I'd ever seen before
His official estimate
of the explosion's power
is nearly 500 kilotons...
More powerful than the blast
from a large nuclear bomb
from the American arsenal
The atomic bomb
dropped on Hiroshima
was about 15 to 20 kilotons,
so 15,000 to 20,000 tons of TNT
So this event, Chelyabinsk, is
about 20 to 30 times that event,
which is what makes it so
unusual but also so destructive
The event is huge
So why didn't we see it coming?
Physicist Mark Boslough
is one of the first scientists
to visit Chelyabinsk
after the meteor strike
He's convinced the answer
is tied up
with the asteroid's trajectory...
The direction it came from
He believes
he can calculate this
with the help
of amateur video footage
Using several key images,
he returns to the precise
locations where they were shot
He has to do this at night
when the stars are out
Well, I am doing
a stellar calibration
So we got
One of our videos
was from a dash cam,
from a car parked
in this parking lot,
and the fireball streaked
across the sky here
We're looking south,
it went from left to right
And what we really want to do
is determine the exact angles
to the fireball
as seen from this location
Mark's goal is to plot the exact
trajectory of the meteor
from where it appears in the sky
Standing where the eye-witness
video was originally taken,
Mark records its GPS coordinates
He then takes a picture of the
night sky with his own camera
He'll use the stars in his photo
to help him pinpoint
the meteor's path in the video
So if the stars show up
on the digital camera,
we can get those angles
and then calibrate that image
that was taken from the dash cam
and know exactly the angles
to the trajectory
of the fireball
By lining up his star field
photo against the video frame,
Mark can get a fix
on where the fireball appeared
relative to the stars
He repeats this process
at several locations
Finally, Mark uses
simple geometry
to locate the fireball
in three-dimensional space,
building a model
that shows exactly the angle
and direction of its approach
Mark's calculations explain
why our telescopes
fail to see
the Chelyabinsk meteor coming:
it approaches from the direction
of the sun
It's masked by the sun's glare
And the Chelyabinsk meteor
is not unusual
Any near-Earth asteroid
is completely invisible
at the point when its orbit
passes between the Earth
and the sun
That's a big gap
in our detection capability
And that's the issue right now
Our current surveys,
the current things
that we're doing right now
to find asteroids
are totally inadequate
We need to bump this up
by about a factor of 100
So we have a problem
Ground-based telescopes
can only detect asteroids
by looking away from the sun
into the night sky
But half the asteroids
that hit us
come from the other direction
There could now be a solution:
putting a telescope into space
Currently, all of the near-Earth
object discoveries
are made with ground-based
optical telescopes
If we could get
above the earth's atmosphere,
we could do a far more
efficient survey
NASA has already demonstrated
the capabilities
of space telescopes
to identify near-Earth objects
In 2010, the WISE mission
detects 135 near-Earth asteroids
before the telescope is retired
The problem is
there may be millions more
Many believe we now need
a longer-term mission
designed for asteroid detection
But the funds
haven't been allocated
Though NASA is rebooting
WISE as an asteroid-hunter,
a tailor-made asteroid
detection system from NASA
looks a long way off
So the private sector
is stepping in
B612, a non-profit foundation,
is financing a new infrared
space telescope
based on existing designs
like this one
Its sole aim: finding more
near-Earth asteroids
Former astronauts Ed Lu
and Rusty Schweikart
are leading the $400 million
fundraising drive
This is a public service
We're a non-profit corporation
We're not doing this
to make money
We're doing this, you know,
to help extend the domain
of life on Earth here
Codenamed Sentinel,
the telescope will orbit the sun
just like Earth
and the other planets
But with a similar orbit
to Venus,
it can look out towards Earth's
path with the sun behind it
Looking away from the sun
will enable it
to detect asteroids
we cannot see from Earth
Sentinel is an infrared
space telescope
that the B612 Foundation
is building,
and we're going to launch it
in 2018
As it moves around
the solar system,
it will scan Earth's orbit,
and we'll discover
just in its first year
200,000 near-Earth objects
Again, compare that
to our current discovery rate
of about a thousand
Sentinel will help
detect asteroids
between Earth and the sun
It will make it easier to find
that potentially dangerous group
of near-Earth asteroids:
not just those
over 140 meters wide,
but also millions
of smaller objects
Historically, these have been
hard to detect
Sentinel's technology
could change that
Sentinel will be built here
by Ball Aerospace,
who also helped design
and produce
the Spitzer and Kepler
Space Telescopes
Program Manager John Troeltzsch
is planning to use their proven
technology in the new telescope
So Sentinel has come in
at the right point in time
We've developed
a lot of technologies
over the last 20 years
in detectors,
in telecommunications systems,
in spacecraft, in solar power
All these things
are coming together today
to help produce
the Sentinel spacecraft
Sentinel's most important
technology
will be its infrared detector
This will find
the smaller asteroids
that most worry scientists
by searching for the heat
they emit
Asteroids are very hard to see
against the dark background
in deep space
Here's a piece of a meteorite
Same composition as an asteroid,
really hard to see
in visible light
However, when I take
my infrared camera,
wow, it shows right up
And I can see it clearly
against the background
This is the advantage
that Sentinel has
for infrared detection
of asteroids
Sentinel's infrared capability
is essential
for detecting small asteroids
Asteroids around a kilometer
across are easier to spot
Even though they're dark,
their size means
they reflect enough sunlight
for us to see them
Smaller dark asteroids
reflect less light,
but infrared detectors
will pick up the heat they emit
That gives Sentinel
a huge advantage
Our design for Sentinel
is designed to find 90%
of 140 meter or larger asteroids
that might threaten the Earth,
the things that can
really destroy
large areas of a continent,
really do major damage
The goal is to launch
Sentinel in 2018
Meanwhile, NASA is helping fund
a ground-based system
to complement existing
telescopes in Hawaii
Codenamed ATLAS, it will provide
a few weeks' warning,
enough for at least some people
to evacuate
Even this won't find every
asteroid that threatens us
Earth is still flying blind
through a solar system
full of undetected asteroids
The nightmare scenario
is still entirely possible
A small asteroid undetected
by our current technologies
could strike at any time
And we now know that the threat
is not just from rocks
140 meters across
Even far smaller asteroid
strikes can be devastating
When scientists use data
from the Chelyabinsk blast
to calculate
the asteroid's size,
they discover it's tiny:
20 meters across,
an asteroid so small,
no one thought
it could cause a problem
In fact, rocks this small
can do far more damage
than we saw at Chelyabinsk
It all depends on four factors:
the asteroid's composition,
its speed, angle of attack,
and where it strikes
In the immediate aftermath
of the Chelyabinsk strike
in Siberia,
physicist Mark Boslough
continues his research
He hunts through the snow
to find meteorites:
fragments of the asteroid
What's amazing to me, though,
when you think about it,
I mean, this is part
of an asteroid
that had been, you know,
floating through space,
orbiting the sun
for billions of years
And two weeks ago,
it exploded in the atmosphere,
dropped to the ground,
and here I am,
holding it in my hand
That's amazing
Mark takes the fragment
to a lab in Yekaterinburg
and studies it
under an electron microscope
There's a crack here
A crack?
Yes
What's the scale on that?
About three microns
Mark's analysis reveals that
the fragment is mostly rock,
and it's shot through
with cracks
These are scars from previous
collisions in space
When it smashed
into our atmosphere
at 40,000 miles per hour,
and reaching more than
3,600 degrees Fahrenheit,
the cracks help break
the meteor apart
The way we understand it is
it hits the atmosphere
going so fast
that there's
so much stress on it
that it actually breaks
the asteroid
It exceeds the strength
of the asteroid,
and that can happen very,
very fast
The Chelyabinsk meteor
disintegrates
15 miles above the ground
It releases a shockwave
with the energy
of almost 30 atom bombs
It's this shockwave
that does the damage
The Chelyabinsk meteor explodes
because it's made
of fractured rock
But not all asteroids
are made this way
Some are made of metal
The Natural History Museum
in London
holds one of the world's largest
collections of meteorites
Caroline Smith studies them,
and it's clear to her that
not all meteorites are alike
Meteorites come in three
different flavors:
stones, stony irons, or irons
These two that I have here,
these are called
stony iron meteorites,
and these are a mixture
of rock and metal
Because they've got
so much metal in them,
they are much heavier than
a normal rock from Earth
I mean, that's a good
sort of 12, 15 kilograms
And this is an iron nickel
meteorite, and it's heavy
This is about
three times as heavy
as the one that
I've just shown you
It does put into context the
type of damage that you can get
from something of that size
Metallic asteroids are denser
and tougher than rocky ones,
so a metallic asteroid the size
of the Chelyabinsk rock
could punch through
the atmosphere
instead of breaking up,
hitting Earth's surface
more or less intact
And here's the proof:
Meteor Crater, Arizona
Over one kilometer across
and more than 150 meters deep,
yet the meteor that creates it
50,000 years ago
is only one-and-a-half times the
size of the Chelyabinsk meteor
The difference is that
it's metallic
It smashes into the ground with
the power of 500 atom bombs
An iron meteorite
slammed into the rock here
with most of its cosmic speed
still intact
at about 40,000 miles per hour
The energy released
in that impact
was something on the order
of ten megatons
of TNT equivalent,
and it's that energy
that was responsible
for excavating this
enormous hole in the ground
and spewing that rock
into the desert around us
Composition makes
a big difference
to the destructive power
of an asteroid
Metallic asteroids
stand the best chance
of surviving
the brutal atmosphere
But even stony asteroids
can still be devastating
Russia, 1908:
a meteor explodes in the sky
above Tunguska, Siberia
Calculations show
that the asteroid
is just twice the width
of the Chelyabinsk rock
But where the Chelyabinsk blast
knocks out windows,
the Tunguska strike flattens
hundreds of square miles
of forest
Its effects are similar
to this nuclear test blast
captured on film
Even 20 years later,
when these images were taken,
the effects are still evident
So why the difference
between the two meteors?
Video images show
the Chelyabinsk asteroid
approaches at a particularly
shallow angle
Mark Boslough feeds that
information into a computer
used to model the behavior
of nuclear weapons
This simulation shows
the effects
of the meteor's trajectory
on its destructive impact
And you get this enormous
fireball,
and that fireball continues
to move downward
and it pushes a shockwave
ahead of it
So these are like
mushroom clouds
with two big, giant nuclear
explosions at the bottom
The shock from the explosion
continues to push forward
and it starts to move downwards
You can see that it's descending
It's down to about
ten kilometers
above the surface here,
at ground zero
The simulation shows that
because the meteor enters
at a shallow angle,
much of the energy
is lost horizontally
The shockwave is destructive,
but it would have been far worse
if had been focused
more downward
and the explosion
had been closer to the ground
This is what Mark believes
happens in Tunguska in 1908
The Tunguska explosion
was much closer to the ground
and it was much more intense
in terms of energy release,
and therefore the blast wave
was much stronger,
and that's why
it blew down trees
over this wide area
almost a thousand square miles
No one dies
in the Tunguska blast,
but only because
no one lives here
Someday, a similar strike
could happen over a city
It could kill millions
I've seen maps
of the Tunguska blast area
overlaid with a map
of Washington, D C,
and it extends beyond
the Beltway in every direction
An asteroid has more damage
potential on the ground
than a nuclear bomb
of the same energy
Fortunately, most asteroids
are relatively small
and strikes are rare
Better detection will help,
but detection alone
is not enough
If we find an asteroid
heading toward Earth,
what can we do about it?
Sci-fi movies
always have the answers
The hero flies up
and blows the asteroid apart
So this is the real
Hollywood way
of looking at an asteroid's
impact hazard mitigation
So they detect,
with just enough time,
that there's this giant asteroid
or comet or something
coming in towards the Earth,
and everyone decides,
"A-ha, well, we're gonna blow it
to kingdom come
We'll just nuke it"
Blowing an asteroid apart
sounds extreme,
but right now, scientists
are exploring ways
to harness technology
to save us from the next
big asteroid strike
We need to think about, "What is
the response of the object?"
"Are we going to fragment it?
"Is that okay?
"Are the fragments
going to recombine
"or fly off out of the way,
"or are fragments
going to hit the Earth
that we need to worry about?"
To learn how these fragments
might behave,
we can simulate a similar impact
here on Earth
And Peter Schultz is the man
who pulls the trigger
He operates one of the few guns
in the world
fast enough to model
an asteroid strike
This hydrogen-powered gun
is targeted into a reinforced
metal safety chamber
Inside this chamber is a small
resin replica of an asteroid
It's there to illustrate
two different approaches
to keeping Earth safe:
destruction and deflection
So today, we're going to do
two experiments
The first one will actually
destroy the asteroid
by using this projectile,
about a quarter inch across
And the second one,
we'll use this projectile:
it's about an eighth inch across
This will not destroy
the asteroid
but instead will form a crater,
and that's really intended
just to deflect it
without destroying it
The aluminum pellets
will hit the asteroid replica
at almost 12,000 miles per hour
That's over three miles
per second
High-speed cameras are needed
to record every millisecond
of the impact
Even this small simulation
will be violent
The team keeps a safe distance
in the control room
High voltage is good
We have ready lights
Oh, jeez!
We really busted the devil
out of this
The high-speed video
allows Peter to analyze
the impact of the larger
projectile in minute detail
Here's the projectile coming in,
you can actually see it
coming in
It's going to hit right there
Boom!
That is just dangerous
Kapow!
There's nothing left except for
something right in the center
The last piece, that core
still could be a threat,
but it's a lot smaller
We're way down
in terms of a threat
So this is one option we got:
we blow the whole thing
to smithereens
But we always have to wonder,
"Is there something left over?"
Scale this up
to blowing apart a real asteroid
and the problem is clear:
deadly fragments of rock
could still rain down on Earth
So the possible problems
with destroying an object,
or disrupting it, we say,
is that you need to have
enough time for the fragments
that are then flying off
in all kinds of directions
to get out of the way before
the Earth passes through there
Blowing an asteroid apart
could make the problem worse
instead of solving it
Luckily, there is another option
Rather than blast
the asteroid apart,
we could use an impact
to change its course
For a lot of objects, you don't
actually need to blow them up
to prevent them from hitting
Earth and making a crater
For me, the most realistic
are what we call
kinetic impactors
for small asteroids,
and that's basically
a cannonball
shot from a spacecraft
to knock it off course
That might reduce
the fragment problem,
but it still needs to be tested
Peter sets up the gun
with a smaller projectile
This shot should create
a crater, but not an explosion
Here we go
Okay, so let's see what we have
Whoa!
Oh, look at that!
This time, the asteroid
stays mostly intact
And this is the crater forming
So what's going to be
interesting is to see,
"Does it make it move?"
Boom!
Then we see that jet come out...
That's really hot gas,
it's a plasma...
And we can see
the ejecta forming,
and now it begins to move
The collision creates a blast
of super-heated impact material
spraying out from the simulated
asteroid
It acts like a rocket
firing out into space
The asteroid is nudged
off course
So the impact hit it,
its momentum
is now shoving this,
and with enough time,
maybe this would get it
out of our way
So I think we're illustrating
that we don't have to destroy
the whole thing to make it move;
we just have to have
enough energy and momentum
to give it a nudge
Could our planet and our lives
be saved by a mere nudge?
The reason it's so easy
is because the Earth's
a moving target
The Earth's about
8,000 miles across,
and it's moving
65,000 miles an hour
So every eight minutes,
the Earth moves a distance
equal to its size
So all I'm really going to do is
upset the timing a little bit
If I make the asteroid show up
at the collision point
three minutes early
or three minutes late,
the Earth's gone,
and that's all it takes,
that's why it's so easy
at large distances
But this would be
a gradual process
The projectile
will have to be launched
many years before the asteroid
comes close to Earth
This is an urgent problem
because if there is
an asteroid out there
that is already on a trajectory
to hit the Earth
and we're not finding out
about it today,
then we're losing
valuable time it takes
to deflect that asteroid,
because what you really need
is time
You need a decade of warning,
and then it's actually
easy to do
But you need time
So there are two clear options
to prevent asteroid strikes:
Blast the asteroid apart
or deflect it
And there is another way
You could do something called
a gravity tractor,
which is something invented
by myself
and an astronaut named Stan Love
And you just hover
a small spacecraft near it
and you tow it
Even an object
as small as a space probe
has its own gravity
It's incredibly weak,
but over time,
it acts like a tow rope,
altering the asteroid's course
Now, it's not as effective
as a kinetic impactor,
but it's controllable
The purpose
of the gravity tractor
is really to fine tune
the deflection
So it appears that we have
the technical capability
to deflect an asteroid
But it will take
a major investment
to prevent the nightmare
scenario:
a small asteroid
we cannot detect
obliterating a major city
And now there's a new question:
could that same technology
be applied
to turn asteroids
from threat to opportunity?
To answer that question,
consider the birth of our planet
I think it's a fairly
widely-held consensus view
that asteroids' initial impacts
with the Earth
four-and-a-half
billion years ago
seeded the Earth
with a veneer of water
and carbon-based materials
that allowed life to form
These are the building blocks
of life
Asteroids probably dumped
organic compounds
onto the early Earth,
and alongside those
may have come
other beneficial materials:
platinum, gold and water,
all valuable resources on Earth
Could asteroids be a new source
of these materials in space?
Chris Lewicki is president
and chief engineer
of Planetary Resources,
a company that hopes to mine
asteroids for profit
We are mining asteroids today
Some of the most productive
metal mines on Earth
are the site of asteroid impacts
hundreds of millions
of years ago
So to go to space,
in some cases, to the source,
we can get these materials
in much more abundance
than they exist naturally
in the Earth's crust
A single asteroid
of between 200 and 500 meters
could contain as much platinum
as we have mined
in the whole of human history
But Planetary Resources
and other companies
are most interested
in another resource:
water locked up
in the asteroid's rock
I think water is the most
important resource
in developing space
because it enables everything
that follows,
and by taking the water
and breaking it
into hydrogen and oxygen,
we can create rocket fuel,
the same rocket fuel that we use
to launch space shuttles
and to explore space
According to Dale Boucher, CEO
of another space mining company,
producing rocket fuel from water
is simple
So now we're making rocket fuel
This is just water in here,
and we've got
a very simple process
run by a couple
of little batteries
passing electric current
through here
We're going to separate
this water into hydrogen,
hydrogen bubbling off this side
And on this side is oxygen
As you can see, there's twice
as much hydrogen as oxygen
because the formula is H20
Many rockets use liquid hydrogen
and oxygen as fuel
Mix them together
and add a spark,
and you get explosive thrust
Okay, so we're going to capture
the hydrogen in this tube,
we're going to bleed
this valve off
All of the hydrogen
that was bubbled off
is coming up in here
Because it's lighter than air,
it will float up
And what we're gonna do
is tilt it like this
and strike a match
We have lift off!
The weight of a rocket
at lift-off is almost all fuel
It burns almost all that fuel
just getting into orbit
If fuel could be produced
from asteroid water,
rockets could maneuver more
easily and even travel faster
This is something
that is abundant in space
On a single 75-meter asteroid,
we have enough water
to have fueled the entire
US space shuttle program
So how would the ability
to refuel in space
affect the future exploration
of our solar system?
In my mind, it makes sense
to go to an asteroid,
mine water, produce rocket fuel
and hold it there
in an orbital station,
let's say,
so that ships or equipment
or robotic missions can stop in,
have a sandwich, have a coffee,
refuel the rocket ship
and go on to Mars
Imagine driving
your car somewhere
without the opportunity
to stop by and gas it up
This is what we've been doing
in exploring space to date
We now have the potential
of being able to refuel
a spaceship on its way
not only from Earth
into outer space
but to refuel
for farther destinations
in the solar system
The rocket fuel is out there
The challenge is to find
the right asteroids,
get to them,
and then extract the water
All of this demands
new technology,
and several companies are
working on that right now
Planetary Resources plan to use
a newly designed telescope
called Arkyd
to find suitable asteroids
Mining in space starts
much the same as mining does
here on Earth
We start with prospecting
and identifying the resource
And we will survey
maybe dozens of asteroids
until we find the one
that has the most interesting
and most economically viable
combination of features
Assuming they find
an asteroid to mine,
the next challenge is
to reach it
Here, the technology for this
is still on the drawing board
NASA is studying ways
to grab an asteroid
and tow it nearer to Earth
This is a very ambitious
engineering project
So the idea is
to send a spacecraft
out to a near-Earth asteroid...
Not to the asteroid belt
outside of Mars,
but to one that actually
on its own comes near Earth
and is small enough...
And then take the asteroid
with a Kevlar bag
And the asteroid, of course,
is spinning relative
to the spacecraft,
and so it would tangle itself up
in the Kevlar,
which would slow it down
and give the spacecraft
something to hold on to
They would then haul it back
and put it into orbit
around the moon
and have someplace
for scientists to go
to look at this large piece
of space rock still in space
For now, it's unclear whether
this program will go forward
But even if the right asteroid
can be found and captured,
the next challenge will be
extracting the resources
Mining expert Dale Boucher
believes there are lessons
from mining on Earth
that will help with the much
tougher task of mining in space
Terrestrial mining is a brute
force type of activity
You know, when we're drilling,
we've got huge 100-pound drills
driving into the rock
with massive air pressure
behind it, trying to excavate
The excavator itself is massive,
weighs many tons
It's using that dead weight
to its advantage
That's what it needs
to get the traction
to push its bucket
into that rock
and pull that rock out of there
None of this will work in space
There's very little gravity,
and the rocks can be cold:
hundreds of degrees below zero
Mining in space demands
whole new technologies
The big difference is gravity,
which means that
we have more problems
with trying to push enough force
on a drill bit, let's say,
or on an excavator bucket
to try and make that
do our work for us
So we have to start thinking
about how we anchor ourselves
to these very virtually
weightless bodies
Dale has been involved
in developing
specialized mining
and drilling technology
to meet these
extraterrestrial challenges
This drill bit
has been designed for use
in the lower temperatures
of the moon
The same technology
might possibly be adapted
for mining asteroids
So this drill is trying to drill
through this simulated
lunar material
that's got water in it,
and we've cooled it down
to liquid nitrogen temperatures
to simulate the temperature
on the surface of the moon,
near the south pole,
where this drill
is supposed to end up
This is different
from the mining drills
used here on Earth
To save energy and weight,
it uses less power
and is much slower
So the drill runs on
about less than
100 watts of power
It takes a very long time
to drill:
it's like watching paint dry
To do a full meter sample
would take about an hour
to an hour-and-a-half,
depending on how hard
the material actually is
Even if the technology
is within reach,
it would be extremely costly
to find suitable asteroids,
relocate them
and extract their resources
Is there a big enough payoff?
If we're going to exploit
asteroids,
I think we need to really do
a cost benefit
It's expensive to get up there
It's plausible
We can do this... after all,
we've been to the moon...
But I think this requires
some very serious study
We know it's possible
to reach an asteroid
and bring samples to Earth
because the Japanese Hayabusa
probe has already done it
But the samples it brought back
in 2010 were microscopic
To mine significant quantities
is an entirely different
challenge
So is the idea of mining
asteroids premature?
Some believe there's no point
in trying to exploit asteroids
until we are safe from them
Well, I can tell you that
you can't mine an asteroid
if you don't know where it is
in the same way you can't
deflect an asteroid
or protect the Earth
from an asteroid
if you don't know where it is
So the first step to all of this
is building Sentinel,
because Sentinel will find the
asteroids in our solar system
We can deal with the threat
of asteroids
and the opportunity that
they present simultaneously
As we develop the technology
to detect, characterize
and ultimately mine asteroids,
it's that very same technology
that will allow us to identify
potentially hazardous asteroids
and take action
This will drive expansion and
exploration of the solar system,
enabling humanity to eventually
live and work and play
in space permanently
A paradox
Are asteroids the biggest threat
humanity faces
or a new opportunity?
As our knowledge
and technology improve,
could it be that they are both?
Captioned by
Media Access Group at WGBH
access wgbh org