Horizon (1964–…): Season 47, Episode 6 - Asteroids: The Good, the Bad, and the Ugly - full transcript
High above us, out in space,
there are millions of very strange,
but very special chunks of rock
tumbling between the planets.
Each one has a different
story to tell.
And those stories are important
to understanding the story
of the solar system.
These are the asteroids...
debris from
an extraordinary event...
..The birth of our solar system,
4.5 billion years ago.
Asteroids ARE fossils
of the early solar system.
They were accumulated from
some of the starting materials
from which everything else was made.
But asteroids continue
to present a threat
to the very future of our planet.
If one of hits, every man woman
and child on the planet could die.
Yet asteroids are about
far more than destruction.
Around the world there are
scientists working to uncover
what these messengers
from the solar system tell us
about our place in the universe.
They essentially
created the solar system we live in
and the planet that we live on.
And what they're finding
is that while asteroids
may not be beautiful,
they do hold a surprising power
over life and death on our planet.
Are we alone in the universe?
Are there other unknown planets
in the outer solar system?
Are the laws of nature
the same everywhere?
Is the solar system stable?
High up above the clouds,
Professor Dave Jewitt dares
to challenge forces of the unknown.
I like mysteries.
I like to think about the things
that are really not understood.
And if I can see some way to do
something to address a problem,
that other people haven't
really followed through with,
then that's what I wanna do.
And right now, he's believes
there is nothing more
intriguing and mysterious
than the tumbling rocks
of the solar system.
If somebody told me 30 years ago
I'd be studying asteroids,
I would've said, "Yeah, you're nuts.
All the hot science is elsewhere."
Why would I spend my time on an
object that basically is not going
to go anywhere in my lifetime?
So, how wrong can you be?
And Dave Jewitt is not alone.
Oh, Gosh. I just love asteroids.
I suppose it makes me geeky, right?
I love the motion,
I love the equations of motion.
I love the way all that works.
We've seen very few
of them up close,
but every time we see a new one,
we learn something new, we find
something we weren't expecting.
Asteroids are the debris
left over from the solar nebula.
They contain the raw
material that never quite
made it to form a planet.
In a way, asteroids are fossils
of the early solar system.
On the Earth, all the materials
we see have been processed
by being sucked into the mantle
and blown out of volcanoes,
and so there's no material on the
Earth which remembers what it was
like when the Earth still formed.
Asteroids are time capsules
that contain information
about the earliest times
in Solar System history,
information that's been lost
from the other planets,
that's been lost from
the Earth, lost from the Moon.
Asteroids have been around,
and they've seen it all.
Asteroids offer tantalising
clues into the earliest moments
of our solar system.
But, for these scientists, the
problem is, how do you get at them?
For the vast majority of asteroids,
we have no information at all,
except the existence of the object
and a guess as to how big it is.
This fuzzy image helps
explain the problem.
This is what an asteroid
looks like through the most powerful
optical telescope on earth.
So how do you begin to study
an object you can hardly see?
Well, one way is to study these.
Tiny fragments of asteroids
that have fallen to earth and
broken apart, called meteorites.
This is it's the oldest thing you
can hold in your hand, really
a piece of history back to the time,
even before the Earth was formed,
way, way before we were ever formed.
Almost everything we know about what
asteroids are actually made of comes
studying these kind of fragments.
Each one has its own history of the
solar system, they're like a puzzle
that we're trying to understand.
We think some asteroids are made of
iron, or at least they were so large
that, when they formed,
they heated and melted.
They could get all
the iron to their core,
just like the Earth has an iron core.
And when we take a big iron meteor,
like this, and slice it open,
the quality of the metal
is really quite amazing.
It's a very pure metal,
nickel iron, some of the oldest
metal in the solar system, in fact.
More than 4. 5 billion years old.
So out there in space,
there are gigantic boulders,
ranging in size from 900 kilometres
to just a few metres and made
of primordial metal and dust.
But the more scientists have
examined the remains of asteroids,
the stranger they get.
It is probably a complete zoo.
And we find the meteorites
have a huge variety of types
and compositions.
And it's telling us that the
asteroids must have a wide
variety of compositions as well.
There is one type in particular
that has opened a door on the
strange and unfamiliar world
that asteroids inhabit out there
in the coldness of space.
We think that most asteroids
are probably like this,
very stony, like the kind of things
we'd find on Earth.
But they have a completely
different chemistry than Earth rocks.
They're put together like
little bits of rocks all reheated,
re-melted and glued together,
And it tells us that
the asteroid belt is a place
with an incredible impact history,
asteroids colliding into each other,
breaking apart, reforming.
And so when we see
these meteorite samples,
it's telling us about that
amazing collision history
in the asteroid belt.
Over 90% of asteroids are found
in an orbit between Jupiter and
Mars, called the main belt.
Almost 200 million kilometres
across, it is home to millions
of these orbiting rocks.
But perhaps the most pressing
question is whether any of them
are on a collision course
with planet Earth.
Arizona's arid desert air
makes it the perfect place
for a very special kind of job.
This is the where people
come to hunt asteroids.
I started out hunting asteroids
about 12 years ago, as an amateur.
I had read an article
in a popular magazine,
and that got me really interested
in the field because not too many
people were working there.
It might not seem it, but Richard
Kowalski is in the front line
of defending planet Earth.
Every night when I come up
to the telescope, I do have it
in the back of my head
that every person on the planet
does have a vested interest
in what I'm doing.
If one hits, there's the potential
that every man, woman and child
on the planet could die.
Richard wants to discover any
asteroids that could be on a
collision course with Earth.
This is our largest telescope
it's a 60-inch or 1.5m F2.
It's the telescope
that we've been using
for approximately five years now.
We discover as many as 3,000
new asteroids every night.
But what Richard fears
is that one of them could create
destruction like this, or worse.
Baringer Crater is just
a few hundred kilometres
from Richard's telescope.
It is 1 kilometre across
and 200 metres deep.
It was made when a 300,000-tonne
asteroid smashed into Earth,
50,000 years ago.
The Earth has been hit in the past
and will be hit again in the future.
What we'd like to do is to
be able to discover these objects
before they hit the Earth.
So, one of the great challenges
for scientists is to understand
what would happen if an asteroid
were to strike planet Earth...now.
Pete Schultz wants
to understand the unique nature
of the explosion caused
if an asteroid were to impact
with the Earth's surface.
It takes a truly odd
piece of equipment.
OK. We're getting close.
This was serial number one, it was
built during the Apollo time,
I guess it's because they thought
there would be several of them made
but this is the first one
and the last one and it's
the only one like it in the world.
This is NASA's vertical gun range.
It was built to study
how impacts affected the moon,
as the astronauts prepared
to make the first lunar landing.
We are armed, gated and reset.
Today, Professor Pete Schultz
uses it to model precisely the
dynamics of an asteroid impact.
We know that these
asteroid impacts are bad,
but you want to understand
really HOW bad.
Schultz uses the NASA gun to fire
projectiles at very high speed
to simulate an asteroid
hitting the Earth.
So for this experiment, we are
going to fire this tiny quarter-inch
aluminium sphere at very high speeds,
up around 5km per second, and we'll
see what kind of crater it produces.
The target it will hit
is made of sand.
So we use sand because it records
the shock effects very clearly.
Outside of the impact chamber
are special, super hi-speed cameras
that can film at up to 1 million
frames per second,
capturing every detail of the impact
and the aftermath for analysis.
OK, lights out. Everything good?
OK, we're out of here.
We have high voltage,
warning lights.
And...rolling.
The ball travels 15 times faster
than the speed of sound.
And it incinerates, exactly
like some asteroids would.
Perfect. Perfect.
Now we're seeing the fire ball
come in,
it's brighter than the sun and then,
kapow, it hits the surface, geez.
This whole region down range
would have been incinerated.
It would have been incinerated
just by this plasma, this exploding
vapour plume, engulfing everything.
There would have been winds that
would have been going so fast,
it could pick up houses and spread
them hundreds of kilometres away.
This would have been armageddon.
Experiments like this
reveal several important things.
One is that it's not just the impact,
it's all that vapour
that runs down range.
In fact, you can see areas here where
there was so much wind it actually
carved out pieces of this landscape.
So what these experiments help us do,
they actually allow us to witness
the event,
see it in real time,
and try to understand
the processes that are going on.
It's really complex
but we have to see it
to understand it.
So asteroid impacts unleash
a trail of destruction
far greater than suggested simply by
the footprint of the crater alone.
It means they are far more complex,
and dangerous,
than many had previously thought.
One of the enduring puzzles,
ever since asteroids were first
discovered 200 hundred years ago,
is why they come anywhere close
to the Earth in the first place.
Most of the time, asteroids
are in a stable orbit
between Mars and Jupiter.
But some go wandering, leaving
their orbit to propel themselves
through space, and coming under the
influence of Jupiter's gravity...
a force that accelerates
them towards Earth.
Scientists have been hunting for
an explanation
for this strange behaviour.
Steve Chesley of NASA's Jet
Propulsion Lab in California
has made a study of a 200 billion
tonne asteroid called Golevka.
This is a model of Golevka,
it's actually about
500 metres across,
say the size of a football stadium.
Um, it rotates in this direction.
As you can see,
it has a very angular shape to it.
He set out to investigate
a 100-year-old theory that said
asteroids were powered
by the sun itself,
what's called the Yarkovsky effect.
The Yarkovsky effect is a very small
acceleration of the asteroid,
and what it is, is, if you take a
model,
you see the sun is hitting
the asteroid,
warming the surface.
As the asteroid rotates,
that hot surface
radiates the heat out
in a different direction into space
and that causes an acceleration,
very slight acceleration
coming from the photons
that are emitted from the asteroid.
The idea is that this acceleration,
slight as it is,
can have significant effect upon
orbit of the asteroid
over millions of years.
It was an intriguing idea.
What sent asteroids
out of their orbit
and on a path towards Earth
was photon propulsion.
But what was lacking,
was proof.
The Arecibo telescope is over
300 metres in diameter.
It's one of the most powerful
telescopes in the world.
And it uses radar to map the precise
position of objects in deep space.
It was this telescope
that would allow Steve Chesley
to detect any tiny alterations
in the orbit of asteroid Golevka
more than
15 million kilometres out in space.
We knew that it would be
in one place
if the Yarkovsky effect wasn't acting
on it,
and would be over here if it was
acting and our models were correct.
When Steve and his team studied the
data the results were unequivocal.
We knew,
from the radar measurements,
where Golevka was within a few tens
of metres
and yet, it was actually
12 or 15 kilometres away
from where it was predicted
to be without the Yarkovsky effect.
So these very precise radar
observations, allowed us to see
the twelve kilometre displacement
caused by the Yarkovsky effect.
So photons, those elementary,
massless, particles of light,
really can create a tiny force.
The force is about
one ounce on Earth -
say the weight of a shot glass
is - that's the force
on this huge asteroid
the size of a football stadium.
Even for me, it's truly remarkable,
it's dramatic, that a force
so slight
can have such dramatic changes
on individual asteroids' orbits
over millions of years.
Steve Chesley's research
means that,
for as long as the sun is shining,
there will be a force that could
send one of those asteroids
hurtling on a journey towards Earth.
Needless to say,
this isn't good news.
But with a threat like this,
what can you do?
Well, for now, there's really only
one thing you can do...
and that's to keep an eye out
for them.
Watching for asteroids is what
Richard Kowalski does,
night after night, at his
observatory in the Arizona desert.
What you can see on this screen
is we have divided
the sky into thousands of areas,
we then choose a number of these
areas into a single block
which will then tell the telescope
to observe
each individual area in succession.
Once it's gotten to the last
area,
it then goes back to the first area
and repeats the process.
Over the course of an hour,
the telescope repeatedly scans
the same areas of the sky.
While the stars appear stationary,
the telescope can spot
any other objects
that change position...
which could be asteroids.
As you can see, on this screen is the
sequence of four images
that came from the telescope.
These objects around the screen
are not moving
so we know that they are stars,
but this object in the centre
is moving and thus we know
that is an asteroid.
The importance of surveying
for near Earth asteroids
is asteroid impact on the Earth
is truly the only natural disaster
that we can actually predict
before it happens.
So whenever Richard finds an
asteroid he thinks could be
on a collision course with Earth,
he immediately files a report.
It goes to the central body
whose job is to monitor
possible asteroid impacts.
Just outside Boston, is the
home of the Minor Planet Centre.
It's director is Tim Spahr
and his job is to keep track of
every asteroid in the solar system.
This is the nerve centre
of the entire asteroid field.
If somebody discovers something,
it has to come through here
and our job is to then distribute
that to the rest of the world.
Asteroids' elusiveness
is part of the thrill.
In some cases,
if you're studying an asteroid
that's moving extremely fast,
er, we ambush it.
We go ahead of where we think it will
be in and set the telescope up
in that area and then hope that it
comes through the field like that.
So, you know,
it's actually ambushing.
And then when you get the asteroid,
then you chase it down and follow it.
Not surprisingly, keeping track
of thousands of objects in the sky
isn't something
that you can do in your head.
Thankfully, help is at hand.
This is really the brains of the
Minor Planet Centre right in here.
This computer system has information
about where asteroids are,
where they will be in the future.
All the observations
all the software is in here.
We definitely need it to be running
all the time, we need it to be safe.
We need everything working here.
Do you feel a sense
of responsibility?
I definitely feel a sense of
responsibility
for keeping a track of the
asteroids. I feel like it's our duty,
it's our task to do that and I do
feel personally responsible for it.
And the task facing Tim,
is growing rapidly.
In 1999, only 10,000 asteroids
were known of.
Since then,
hundreds of thousands more,
of all shapes and sizes,
have been discovered.
Tim has developed a map to
visualise their location.
And on that map,
there's one class of asteroid
he's concerned with above all -
those near-Earth asteroids
closest to our planet.
On the screen here is a map
of the solar system.
The Sun in the centre, and the third
planet up there would the Earth.
The red dots in here are actually
near-Earth asteroids,
the green ones
are the regular main belt asteroids.
There are over 7,000 near-Earth
asteroids,
but there's one type they are
particularly concerned to locate.
Those asteroids that are
over one kilometre in diameter.
These are the monsters of the skies.
An Earth impact with one of these
would spell catastrophe
for the planet.
If a one-kilometre diameter asteroid
were to hit, say, New York City,
that would very likely affect people
in you know, 100 miles away.
It might kill people 100 miles away.
So you're talking, really,
a catastrophe, instantaneously,
as soon as it hits.
Tim's data reveals
that there are 900 asteroids
bigger than a kilometre
in those dangerous
near-Earth orbits.
But the big question -
are any of them
on a collision course with Earth?
Right now,
there's no information
that any of those large objects
will
hit the Earth in the next 100 years.
So we're safe from impacts of
those objects for at least 100 years.
But there are still smaller asteroids
than one kilometre
that we have not yet discovered.
So I can't say we're safe from them
because we don't know
where they are, just yet.
So, for now, we are safe from a
catastrophic asteroid impact.
Even if the thousands of smaller
asteroids might still pose a threat.
However another group of scientists
have a very different mystery
about asteroids to investigate.
One that may help solve
one of the greatest quandaries
about life on Earth.
This is Maunu Kea
in Hawaii. It is home
to some of the most
powerful telescopes in the world.
For 30 years, Professor Dave Jewitt
has used them to probe deep
into the solar system.
And once Dave
interrogates deep space,
it's rarely ever the same again.
In 1992,
I discovered the first objects
found beyond Neptune
since Pluto.
The biggest discovery
in the solar system
since
the discovery of the asteroids.
It was a discovery that led to Pluto
losing its status as a planet,
something the world had taken
for granted for over 60 years.
It established Dave's reputation
as a pioneering astronomer.
It's important not to work on things
that other people are working on.
All you'll do is get the same result
as everybody else. You won't make
any discoveries, you'll just
confirm what is already known.
Dave's desire to journey
where others fear to tread
has led him to this.
This bright dot with a long
hazy tail is called Elst-Pizarro.
It was found alongside all the other
asteroids in the asteroid belt.
The problem was, it just
didn't look like an asteroid.
So why did it seem so out of place?
it didn't look like the other
asteroids so it was a freak.
And it got a lot of attention
straightaway,
because it was
such a remarkable object.
Nobody had seen
anything like that before.
What had got them excited
was that to astronomers,
asteroids normally look like this.
Just a point of light.
No dust cloud,
and definitely no tail.
For years Elst-Pizarro,
with its orbit of an asteroid
but strange fuzzy appearance,
left scientists baffled.
Until finally,
someone suggested an explanation.
Finally, a paper came out saying
it must be due to the
collision between two asteroids.
So two asteroids
slammed into each other
with high speed, and shattered
and produced a cloud of dust.
So the strange tail was thought
to be the debris from a collision
between Elst-Pizarro
and another asteroid.
And, very quickly,
most of the scientific world
forgot about Elst-Pizarro.
But Dave didn't.
He had a hunch that there was more
to this puzzling little light
in the sky than at first appeared.
A hunch that, if proved correct,
might help solve one of the great
mysteries of life here on Earth.
Dave decided to investigate,
and began looking for
someone to work with.
Somebody with a head
for the challenge.
When Dave suggested that
I look at this object, I didn't
actually know anything about it.
Nothing had really been said about it
in the last 6 years since
it's been discovered,
so I just decided, OK, it's just an
interesting thing to take a look at.
Dave and Henry knew that if
Elst-Pizarro's fuzzy tail really
had been caused by a collision
the debris should
have dispersed by now,
and Elst-Pizarro should look
like a normal asteroid again.
But when they looked again,
what they saw was that
the tail was still there.
It was strong evidence
the collision theory was wrong.
Collisions are very, very rare.
Either Elst-Pizarro is
the unluckiest asteroid in the solar
system, that keeps getting whacked
and producing dust in that way,
which doesn't make any sense,
or there's another mechanism
for producing the dust.
Elst-Pizarro's appearance
remained an anomaly.
Dave and Henry realised
that if they were going to make
any real sense of it
they needed to find
another example of an asteroid
behaving in the same strange way.
Dave and Henry's problem
was that, in the 200 years
since asteroids were discovered,
Elst-Pizarro
was the only one like it.
Finding another one could be
a complete wild goose chase.
Using the giant telescopes on
Mauna Kea, Dave and Henry began to
hunt through the asteroid belt.
For four years, they
scanned the skies.
They studied 300 more asteroids.
All of them looked identical...
..except for one.
When we saw these images, I didn't
know what to think actually.
Maybe this is what we've been
looking for all this time.
But we were maybe just a bit nervous.
You know, we may be on the...
the cusp of something big.
What they'd seen was an asteroid
sporting a tiny, faint
fan-shaped tail.
Just like with Elst-Pizarro, they
were convinced it was impossible
this tail was created by
a collision between asteroids.
They had another explanation
that to many seemed unthinkable.
This is an image of a comet.
They are objects that are thought
to have been born
in the freezing
outer reaches of the solar system.
They have long, elliptical orbits
that bring them towards
the sun and the Earth.
And in comets
the tail is a sign of something
very special inside the centre.
Ice.
Their appearance is due to
the vaporisation of the ice, that
blows material off to make a tail.
So they have this distinctive
appearance, basically of having
a long tail of dust.
For 200 years
the asteroid belt was thought to be
an orbiting collection of dry
lumps of rock and metal.
Dave and Henry's new idea was that
those asteroids they had observed
might look fuzzy
and have tails because they too
actually had ice inside them.
It was a radical suggestion, because
scientists had always thought
asteroid orbits were far too close
to the sun for them to be icy.
People were uncomfortable,
because of this prevailing idea
that the asteroids are rocky,
and the comets are icy, and there
should be nothing in-between.
The reason why ice
in the asteroids mattered so much
is that it could help explain
something that makes our planet
unique in the solar system.
Our beautiful blue planet
is the only one to have
an abundant supply of liquid water.
Around 70% of the Earth's surface
is covered by the oceans.
But there has always been a mystery
as to where all this water
actually came from.
For a decade, Dave Jewitt has
been investigating this problem,
because scientists have established
that when Earth formed,
over 4.5 billion years ago,
it used to be a very different
kind of place.
The early Earth was really hot.
It formed from hot material
in orbit around the sun.
So hot that we think the entire
surface of the Earth
was covered by liquid lava for
the first 100 million years,
a bit like
the land that we see behind us.
Dave believes
the searing heat of molten rock
would have had a profound effect
on the Earth's early climate.
Because it was so hot, we also think
the early Earth was very dry.
It's like putting something in the
oven and baking it for too long.
It comes out bone dry. We think the
Earth was bone dry when it formed.
That would means that the lush, wet
climate that we enjoy today
must be the result of some
dramatic events long after
the Earth was born.
The Earth got its water some time
after it had formed and cooled down,
by being hit by objects that
carried water from somewhere
else in the solar system.
If Dave and Henry were right,
a constant stream of icy
asteroids hitting the early Earth
could have played a vital role
in bringing our planet its water.
But for all their observations,
they hadn't actually seen ice
on an asteroid.
So the one problem with our
observations is that they only
told us what the object looked like
and with that information we knew...
we thought we could only explain it
with the presence of ice
but we couldn't actually prove that
that was the case.
The last piece of the jigsaw
finally arrived early this year,
with help from the mighty
telescopes of Maunu Kea.
Andy Rivkin
makes the invisible visible,
by using a NASA telescope to look
at objects using infrared light.
The infrared part of the spectrum
is useful
because it contains
information about the composition of
asteroids and other objects,
and so by observing there you get
a better handle on the composition
than you would
if you observed only in the visible.
Andy studies the shape of
the infrared spectrum reflected off
the surface of asteroids,
because tiny differences
in the peaks and troughs can reveal
what the surface is made of.
Andy became interested
in an asteroid called 24 Themis.
The shape of its spectrum
meant something very odd must
be happening at its surface.
We started by comparing it to other
materials and objects that
we thought might be similar.
We tried comparing it to other
asteroids, but it didn't look like
any of the other asteroids.
We tried comparing it to meteorites,
and it didn't look like
any other meteorites.
So we knew we had to come up with
some other explanation.
Finally, in April this year,
Andy and his team
published their explanation
as to why 24 Themis gives off
such a strange kind of light.
We found that water ice was
actually the best choice, and
that was really exciting, because
it was the first time, certainly that
we knew of, that anyone had found
water ice out in the asteroid belt.
Even though it had been
suspected for some time
that it could be out there,
no-one had ever seen it.
Andy had finally proved
an asteroid really could be icy.
It now seems certain
the strange behaviour and tails
seen by Dave and Henry on their
asteroids was caused by ice too.
DAVE: I think any time you make
a discovery it's exciting.
Any time you find a new thing,
it's a big thrill.
Definitely a big thrill, yeah.
Cos it's hard.
It means that asteroids
could have played
one of the most important roles
in creating the Earth we see today.
We know that asteroids did hit
the Earth, for billions of years.
The question is what the asteroids
brought with them.
We previously thought
mostly rock and metal.
Now we understand that the asteroids
would also have brought
a lot more water and ice than we'd
previously suspected.
These discoveries are starting
to change our understanding
of the solar system.
Water and ice really are abundant
in the asteroid belt.
And that maybe water and ice
is more abundant throughout
the entire inner solar system.
Finding the water in the asteroid
belt is the key to starting to change
our thinking about where
Earth's water may have come from.
Astronomers still don't know
how much of Earth's water
came from asteroids
and how much from other
sources of ice such as comets.
Without that water, of course,
life on Earth could not exist.
Which provokes what is perhaps
the most intriguing question of all.
Did asteroids play a role
in the creation of life?
Not far from San Francisco,
California,
there are scientists
pondering this very question.
Scott Sandford wants to investigate
whether the basic chemicals of life
could have been formed in space,
perhaps even on an asteroid.
So he's created the conditions
of deep space in a machine.
This machine has been developed
to allow us to simulate
environmentsthat are out in space,
either in the interstellar medium,
events where stars form,
or the environments, let's say,
in the icy satellites of planets
in the outer solar system.
Environments that
have low temperatures, no air,
so vacuum, and high radiation fields.
He wants to see if the complex
carbon molecules that are essential
to life
could be created from the much
simpler chemicals found in space.
In this chamber is a sample probe
covered in a tiny layer of water,
methanol and pyrimidine
that is frozen to just 20 degrees
above absolute zero, and exposed to
intense ultraviolet light.
In this particular experiment we're
looking at whether certain conditions
will form one of the nucleobases,
so one of the molecules
that makes up our DNA.
And from his analysis of samples
from experiments like this,
Scott has made
a remarkable discovery.
By processing ices of the type
we see out in space, we can make
some of the building blocks that
we see in biology on the Earth today.
We're making the building blocks
of life, that's what we're finding.
Just because you can create these
building blocks of life in a lab,
it doesn't mean it really happens
on an asteroid.
So Scott has carefully examined
meteorite samples to see if they
contain traces of these chemicals.
In some classes
of meteorites, which we think
come from asteroids, we find a
variety of organic compounds.
And these include things that
some people are familiar with,
like amino acids, the building
blocks of proteins in our bodies,
but also materials
like the nucleobases,
the building blocks of DNA.
So hidden within the rock
could have been the materials
that made possible
the emergence of life on Earth.
And that means that when asteroids
struck Earth billions of years ago
they could have completely
transformed our planet.
Asteroids could have played
an important role in getting
life started on Earth
by delivering the raw starting
materials that we need to get
everything going to get life started.
It seems the story of life on Earth
is inextricably linked
to the story...
of asteroids.
The possibility that asteroids
hold the key to some of the deepest
mysteries about our planet explains
why scientists have always dreamt of
reaching out into space and bringing
back a pristine asteroid sample.
And earlier this year, that
wish may finally have come true.
In June, one of the strangest space
missions in history came to an end.
It might look like a
firework display, but this
is actually a Japanese spacecraft
re-entering the Earth's atmosphere.
Seven years after it first left
the Earth, the Hayabusa probe
landed in the Australian desert.
The scientific team were
careful to handle the crashed
probe with extreme caution.
Because within this small container
is what scientists hope will be the
first ever asteroid sample
collected directly from space.
The sample consists a lot of little
grains, and some of the grains
are as small as ten microns,
so ten millionths of a metre across,
so this is a particle smaller
than the width of a human hair.
Even in a microscope it looks
like a dot, OK, and so, um,
the analyses of such small samples
is obviously complicated.
Obviously our hope is that some
of that material really is from
the asteroid,
but at this point we don't
know for sure one way or the other.
It may be months or even years,
before the team discovers what
if anything these grains can reveal.
While many scientists
are excited about what
asteroids might tell us about
the beginnings of life on Earth,
new research suggests that it is how
asteroids might put an end to life
that should really concern us.
On the 6th of October 2008
asteroid hunter Richard Kowalski
saw something that would
help change the assessment
of the threat presented by
asteroid impacts.
The night was proceeding
normally and up on the screen
came another asteroid.
As I continued to make observations
throughout the night it appeared
to be moving slightly faster.
And this indicates that the
object is close to the Earth.
As with any other asteroid,
Richard reported what he'd found
to the Minor Planet Center.
I got up in the morning,
about 7 o'clock.
I had a message from the computer
saying, "could not compute
an orbit for a particular object".
I grabbed the observations of
this object and I computed an orbit
and it was immediately apparent,
right then, that that object
was going to hit the Earth.
and sort of ominous fashion,
it said it was in 19 hours.
Following a strict written protocol,
Tim quickly reported the findings
to NASA's asteroid
investigation team in California.
We got a call from Tim Spahr
at the Minor Planet Center
saying we had an
impacter coming in, in less than
24 hours.
So that woke me up.
NASA's expert on asteroid orbits,
Steve Chesley, immediately
started to verify the data.
Steve The first thing I saw
was a 1.000,
100% probability of impact
and erm, in less than a days' time.
This I'd never seen,
anything like this outside of
simulations and software testing.
An asteroid strike
would create a huge explosion.
NASA feared this might be mistaken
for a nuclear bomb.
We wanted folks to know that this
was a natural event by mother nature
rather than some sort of a
man-made event like a missile
or something dreadful.
Information passed rapidly
up the chain of command.
So, NASA headquarters
notified the Whitehouse
that this was coming.
Everyone wanted to know
where it would strike
NASA predicted a remote
area of the Nubian desert.
AT quarter to three in the morning,
NASA were proved right.
The explosion created a vast
fireball burning as hot as the sun.
It was so big and so hot, this image
was captured by a weather satellite.
As dawn broke,
the smoke trail it left behind was
still visible from the ground.
I definitely think
the impact was a wake-up call.
I have to admit I never thought I'd
see that in my career, where we would
discover something that would
hit the Earth later that day.
What makes this impact so worrying
is that this asteroid was too small
for anyone to see until it was
very, very close to the Earth
For one scientist, it's was
a salutary reminder that
we cannot afford to ignore the
threat posed by small asteroids.
Physicist Mark Boslough uses
one of the world's most powerful
supercomputers to study the hazards
facing our planet, from climate
change to nuclear explosions.
But for years, he's been fascinated
by a strange event at the
beginning of the last century,
and what it might tell us about
the threat of asteroid impacts.
On June 30th 1908, without warning,
a massive explosion wiped out
over 1,500 square kilometres
of Siberian forest.
Millions of trees were destroyed.
Scientists thought it had been
caused by an asteroid strike.
But then why was there no sign
of any kind of impact crater?
The answer is that the devastation
had to be caused by an asteroid
attack of a very particular kind.
The explosion was caused by an
asteroid that entered the atmosphere,
got close to the surface and
exploded before it hit the ground.
That explosion created a blast wave
with hurricane-force winds
that knocked trees over
for thousands of square miles.
Scientists call it an air burst - a
massive explosion in the atmosphere
rather than on the ground.
As it enters the atmosphere
at speeds of up to
20 kilometres per second
the air resistance decelerates the
asteroid so fast it breaks
apart in a huge explosion.
And crucially,
it is small asteroids that are most
likely to explode in this way.
Most of the damage from an explosion
like this is actually the blast
waves, it's the very high winds.
Based on the physics
of nuclear explosions,
the original air burst model
estimates the Tunguska explosion
must have been 1,000 times bigger
than the nuclear bombs
at Hiroshima and Nagasaki.
But crucially,
the air burst model suggests the
asteroid would have packed this huge
destructive force
even though it was as small
as 100 metres in diameter.
But Mark realised there
was another problem.
The model was ignoring a crucial
difference between nuclear bomb
air bursts, and asteroids.
Asteroids are extremely heavy
and move so fast that
they carry huge momentum
He created a new simulation to
investigate the effect this would
have on their destructive power.
In this simulation I include more of
the physics to be more realistic,
you can see that the main shockwave
doesn't come out of the point of the
explosion, but it comes out from the
point where the fireball descends to.
so by the time the shockwave hit
the ground it's much stronger
than it would otherwise be so
there is more damage on the ground,
because the destructive
power was carried downward.
Based on Mark's new calculations,
the devastation at Tunguska
could have been caused
by an asteroid only one third as
large as previous estimates.
Perhaps as small as 30-50
metres in diameter.
And for him this carries
a worrying implication.
Smaller asteroids are more
dangerous than we used to think
and because there are so many
more smaller asteroids than bigger
asteroids we need to take that risk
more seriously than we used to.
Mark's work means scientists
may have to redraw the
asteroid threat map.
If a Tunguska scale asteroid
exploded over London or New York it
would be very destructive, it would
be as destructive as a nuclear bomb
exploding over one of those cities.
Scientists estimate that there
could be over a million of these
kinds of asteroids up in space.
But nobody knows where they are,
or where they are headed.
A 2010 report by the American
National Academies of Sciences,
was so concerned
about the potential threat
to Earth from the smallest kind of
asteroids, that it has called for
a new survey to track them down.
The problems is that even for
dedicated asteroid hunters like
Richard Kowalski,
they are extremely hard to find.
Many of them are as dark as a
charcoal briquette and we see
them by reflected sunlight.
So you can imagine a 100-metre
charcoal briquette out in space
is going to be kind of hard to see.
And that means that if an asteroid
like this is heading for Earth,
we might only see it when it is very
close, with very little warning.
There's a reasonable chance that
you'll see it for the first time, on
it's terminal trajectory, just
days, or weeks, before the impact.
If that were to happen,
there is nothing that anyone could
to stop it from hitting the Earth.
For the public authorities, the
only option, would be to try to get
the thousands or even millions
of people out of the impact zone.
I think Katrina, Hurricane Katrina,
really illustrated how hard it
is to evacuate a large area.
It's not set up that we have an
asteroid evacuation plan
in place right now.
I know it's been discussed at the UN,
but if we were to be
issued 3 days' warning, I really
don't know what would happen.
And it wouldn't be very good.
I'm sure we're not
ready for that yet.
However far away they may be,
and however difficult to find,
scientists now understand that
Earth's past
and its future cannot be separated
from these tiny rocks of destiny.
The quest to understand them will
continue on Earth and from space.
NASA currently has a spacecraft
en route to visit two
of the largest asteroids
in the solar system.
It will arrive in July 2011.
And President Obama has challenged
NASA to send astronauts to an
asteroid by 2025.
200 years after
they were first discovered,
solar system science has finally
entered the age of the asteroids.
The good, the bad and the ugly.
Are asteroids bad, good or ugly?
I'd say all of the above.
I wouldn't say that asteroids
are good or bad.
They essentially created the solar
system we live in
and the planet that we live on.
They've shaped the Earth in ways,
it's safe to say,
humans wouldn't be around
but for the asteroid impact.
I take asteroids like people -
I take them as I find them
and try to learn their
individual foibles.
I think ultimately asteroids will be
our friends
because they have the capability
of giving us resources for use
as we try to explore
and extend our reach into space.
Asteroids are certainly not ugly.
Asteroids are beautiful.
The ones that we don't understand, I
think that makes them more beautiful.
That's the beauty of science.
That's why we keep doing it.
It's to try to learn more things and
when we get a curve ball thrown in,
that's part of the process.
That's the fun.
I have an asteroid named after
myself. It's (2956) Yeomans.
That's quite a hoot.
I do have an asteroid
and this is it.
(17857) Hsieh 1998KR1
I have an asteroid. It's called
(6434) Jewitt. It makes me feel like
I'm part of the cosmos.
I have an asteroid named after me.
Pete Schulz. It looks like I've got
a bullet with my name on it.
HE LAUGHS
there are millions of very strange,
but very special chunks of rock
tumbling between the planets.
Each one has a different
story to tell.
And those stories are important
to understanding the story
of the solar system.
These are the asteroids...
debris from
an extraordinary event...
..The birth of our solar system,
4.5 billion years ago.
Asteroids ARE fossils
of the early solar system.
They were accumulated from
some of the starting materials
from which everything else was made.
But asteroids continue
to present a threat
to the very future of our planet.
If one of hits, every man woman
and child on the planet could die.
Yet asteroids are about
far more than destruction.
Around the world there are
scientists working to uncover
what these messengers
from the solar system tell us
about our place in the universe.
They essentially
created the solar system we live in
and the planet that we live on.
And what they're finding
is that while asteroids
may not be beautiful,
they do hold a surprising power
over life and death on our planet.
Are we alone in the universe?
Are there other unknown planets
in the outer solar system?
Are the laws of nature
the same everywhere?
Is the solar system stable?
High up above the clouds,
Professor Dave Jewitt dares
to challenge forces of the unknown.
I like mysteries.
I like to think about the things
that are really not understood.
And if I can see some way to do
something to address a problem,
that other people haven't
really followed through with,
then that's what I wanna do.
And right now, he's believes
there is nothing more
intriguing and mysterious
than the tumbling rocks
of the solar system.
If somebody told me 30 years ago
I'd be studying asteroids,
I would've said, "Yeah, you're nuts.
All the hot science is elsewhere."
Why would I spend my time on an
object that basically is not going
to go anywhere in my lifetime?
So, how wrong can you be?
And Dave Jewitt is not alone.
Oh, Gosh. I just love asteroids.
I suppose it makes me geeky, right?
I love the motion,
I love the equations of motion.
I love the way all that works.
We've seen very few
of them up close,
but every time we see a new one,
we learn something new, we find
something we weren't expecting.
Asteroids are the debris
left over from the solar nebula.
They contain the raw
material that never quite
made it to form a planet.
In a way, asteroids are fossils
of the early solar system.
On the Earth, all the materials
we see have been processed
by being sucked into the mantle
and blown out of volcanoes,
and so there's no material on the
Earth which remembers what it was
like when the Earth still formed.
Asteroids are time capsules
that contain information
about the earliest times
in Solar System history,
information that's been lost
from the other planets,
that's been lost from
the Earth, lost from the Moon.
Asteroids have been around,
and they've seen it all.
Asteroids offer tantalising
clues into the earliest moments
of our solar system.
But, for these scientists, the
problem is, how do you get at them?
For the vast majority of asteroids,
we have no information at all,
except the existence of the object
and a guess as to how big it is.
This fuzzy image helps
explain the problem.
This is what an asteroid
looks like through the most powerful
optical telescope on earth.
So how do you begin to study
an object you can hardly see?
Well, one way is to study these.
Tiny fragments of asteroids
that have fallen to earth and
broken apart, called meteorites.
This is it's the oldest thing you
can hold in your hand, really
a piece of history back to the time,
even before the Earth was formed,
way, way before we were ever formed.
Almost everything we know about what
asteroids are actually made of comes
studying these kind of fragments.
Each one has its own history of the
solar system, they're like a puzzle
that we're trying to understand.
We think some asteroids are made of
iron, or at least they were so large
that, when they formed,
they heated and melted.
They could get all
the iron to their core,
just like the Earth has an iron core.
And when we take a big iron meteor,
like this, and slice it open,
the quality of the metal
is really quite amazing.
It's a very pure metal,
nickel iron, some of the oldest
metal in the solar system, in fact.
More than 4. 5 billion years old.
So out there in space,
there are gigantic boulders,
ranging in size from 900 kilometres
to just a few metres and made
of primordial metal and dust.
But the more scientists have
examined the remains of asteroids,
the stranger they get.
It is probably a complete zoo.
And we find the meteorites
have a huge variety of types
and compositions.
And it's telling us that the
asteroids must have a wide
variety of compositions as well.
There is one type in particular
that has opened a door on the
strange and unfamiliar world
that asteroids inhabit out there
in the coldness of space.
We think that most asteroids
are probably like this,
very stony, like the kind of things
we'd find on Earth.
But they have a completely
different chemistry than Earth rocks.
They're put together like
little bits of rocks all reheated,
re-melted and glued together,
And it tells us that
the asteroid belt is a place
with an incredible impact history,
asteroids colliding into each other,
breaking apart, reforming.
And so when we see
these meteorite samples,
it's telling us about that
amazing collision history
in the asteroid belt.
Over 90% of asteroids are found
in an orbit between Jupiter and
Mars, called the main belt.
Almost 200 million kilometres
across, it is home to millions
of these orbiting rocks.
But perhaps the most pressing
question is whether any of them
are on a collision course
with planet Earth.
Arizona's arid desert air
makes it the perfect place
for a very special kind of job.
This is the where people
come to hunt asteroids.
I started out hunting asteroids
about 12 years ago, as an amateur.
I had read an article
in a popular magazine,
and that got me really interested
in the field because not too many
people were working there.
It might not seem it, but Richard
Kowalski is in the front line
of defending planet Earth.
Every night when I come up
to the telescope, I do have it
in the back of my head
that every person on the planet
does have a vested interest
in what I'm doing.
If one hits, there's the potential
that every man, woman and child
on the planet could die.
Richard wants to discover any
asteroids that could be on a
collision course with Earth.
This is our largest telescope
it's a 60-inch or 1.5m F2.
It's the telescope
that we've been using
for approximately five years now.
We discover as many as 3,000
new asteroids every night.
But what Richard fears
is that one of them could create
destruction like this, or worse.
Baringer Crater is just
a few hundred kilometres
from Richard's telescope.
It is 1 kilometre across
and 200 metres deep.
It was made when a 300,000-tonne
asteroid smashed into Earth,
50,000 years ago.
The Earth has been hit in the past
and will be hit again in the future.
What we'd like to do is to
be able to discover these objects
before they hit the Earth.
So, one of the great challenges
for scientists is to understand
what would happen if an asteroid
were to strike planet Earth...now.
Pete Schultz wants
to understand the unique nature
of the explosion caused
if an asteroid were to impact
with the Earth's surface.
It takes a truly odd
piece of equipment.
OK. We're getting close.
This was serial number one, it was
built during the Apollo time,
I guess it's because they thought
there would be several of them made
but this is the first one
and the last one and it's
the only one like it in the world.
This is NASA's vertical gun range.
It was built to study
how impacts affected the moon,
as the astronauts prepared
to make the first lunar landing.
We are armed, gated and reset.
Today, Professor Pete Schultz
uses it to model precisely the
dynamics of an asteroid impact.
We know that these
asteroid impacts are bad,
but you want to understand
really HOW bad.
Schultz uses the NASA gun to fire
projectiles at very high speed
to simulate an asteroid
hitting the Earth.
So for this experiment, we are
going to fire this tiny quarter-inch
aluminium sphere at very high speeds,
up around 5km per second, and we'll
see what kind of crater it produces.
The target it will hit
is made of sand.
So we use sand because it records
the shock effects very clearly.
Outside of the impact chamber
are special, super hi-speed cameras
that can film at up to 1 million
frames per second,
capturing every detail of the impact
and the aftermath for analysis.
OK, lights out. Everything good?
OK, we're out of here.
We have high voltage,
warning lights.
And...rolling.
The ball travels 15 times faster
than the speed of sound.
And it incinerates, exactly
like some asteroids would.
Perfect. Perfect.
Now we're seeing the fire ball
come in,
it's brighter than the sun and then,
kapow, it hits the surface, geez.
This whole region down range
would have been incinerated.
It would have been incinerated
just by this plasma, this exploding
vapour plume, engulfing everything.
There would have been winds that
would have been going so fast,
it could pick up houses and spread
them hundreds of kilometres away.
This would have been armageddon.
Experiments like this
reveal several important things.
One is that it's not just the impact,
it's all that vapour
that runs down range.
In fact, you can see areas here where
there was so much wind it actually
carved out pieces of this landscape.
So what these experiments help us do,
they actually allow us to witness
the event,
see it in real time,
and try to understand
the processes that are going on.
It's really complex
but we have to see it
to understand it.
So asteroid impacts unleash
a trail of destruction
far greater than suggested simply by
the footprint of the crater alone.
It means they are far more complex,
and dangerous,
than many had previously thought.
One of the enduring puzzles,
ever since asteroids were first
discovered 200 hundred years ago,
is why they come anywhere close
to the Earth in the first place.
Most of the time, asteroids
are in a stable orbit
between Mars and Jupiter.
But some go wandering, leaving
their orbit to propel themselves
through space, and coming under the
influence of Jupiter's gravity...
a force that accelerates
them towards Earth.
Scientists have been hunting for
an explanation
for this strange behaviour.
Steve Chesley of NASA's Jet
Propulsion Lab in California
has made a study of a 200 billion
tonne asteroid called Golevka.
This is a model of Golevka,
it's actually about
500 metres across,
say the size of a football stadium.
Um, it rotates in this direction.
As you can see,
it has a very angular shape to it.
He set out to investigate
a 100-year-old theory that said
asteroids were powered
by the sun itself,
what's called the Yarkovsky effect.
The Yarkovsky effect is a very small
acceleration of the asteroid,
and what it is, is, if you take a
model,
you see the sun is hitting
the asteroid,
warming the surface.
As the asteroid rotates,
that hot surface
radiates the heat out
in a different direction into space
and that causes an acceleration,
very slight acceleration
coming from the photons
that are emitted from the asteroid.
The idea is that this acceleration,
slight as it is,
can have significant effect upon
orbit of the asteroid
over millions of years.
It was an intriguing idea.
What sent asteroids
out of their orbit
and on a path towards Earth
was photon propulsion.
But what was lacking,
was proof.
The Arecibo telescope is over
300 metres in diameter.
It's one of the most powerful
telescopes in the world.
And it uses radar to map the precise
position of objects in deep space.
It was this telescope
that would allow Steve Chesley
to detect any tiny alterations
in the orbit of asteroid Golevka
more than
15 million kilometres out in space.
We knew that it would be
in one place
if the Yarkovsky effect wasn't acting
on it,
and would be over here if it was
acting and our models were correct.
When Steve and his team studied the
data the results were unequivocal.
We knew,
from the radar measurements,
where Golevka was within a few tens
of metres
and yet, it was actually
12 or 15 kilometres away
from where it was predicted
to be without the Yarkovsky effect.
So these very precise radar
observations, allowed us to see
the twelve kilometre displacement
caused by the Yarkovsky effect.
So photons, those elementary,
massless, particles of light,
really can create a tiny force.
The force is about
one ounce on Earth -
say the weight of a shot glass
is - that's the force
on this huge asteroid
the size of a football stadium.
Even for me, it's truly remarkable,
it's dramatic, that a force
so slight
can have such dramatic changes
on individual asteroids' orbits
over millions of years.
Steve Chesley's research
means that,
for as long as the sun is shining,
there will be a force that could
send one of those asteroids
hurtling on a journey towards Earth.
Needless to say,
this isn't good news.
But with a threat like this,
what can you do?
Well, for now, there's really only
one thing you can do...
and that's to keep an eye out
for them.
Watching for asteroids is what
Richard Kowalski does,
night after night, at his
observatory in the Arizona desert.
What you can see on this screen
is we have divided
the sky into thousands of areas,
we then choose a number of these
areas into a single block
which will then tell the telescope
to observe
each individual area in succession.
Once it's gotten to the last
area,
it then goes back to the first area
and repeats the process.
Over the course of an hour,
the telescope repeatedly scans
the same areas of the sky.
While the stars appear stationary,
the telescope can spot
any other objects
that change position...
which could be asteroids.
As you can see, on this screen is the
sequence of four images
that came from the telescope.
These objects around the screen
are not moving
so we know that they are stars,
but this object in the centre
is moving and thus we know
that is an asteroid.
The importance of surveying
for near Earth asteroids
is asteroid impact on the Earth
is truly the only natural disaster
that we can actually predict
before it happens.
So whenever Richard finds an
asteroid he thinks could be
on a collision course with Earth,
he immediately files a report.
It goes to the central body
whose job is to monitor
possible asteroid impacts.
Just outside Boston, is the
home of the Minor Planet Centre.
It's director is Tim Spahr
and his job is to keep track of
every asteroid in the solar system.
This is the nerve centre
of the entire asteroid field.
If somebody discovers something,
it has to come through here
and our job is to then distribute
that to the rest of the world.
Asteroids' elusiveness
is part of the thrill.
In some cases,
if you're studying an asteroid
that's moving extremely fast,
er, we ambush it.
We go ahead of where we think it will
be in and set the telescope up
in that area and then hope that it
comes through the field like that.
So, you know,
it's actually ambushing.
And then when you get the asteroid,
then you chase it down and follow it.
Not surprisingly, keeping track
of thousands of objects in the sky
isn't something
that you can do in your head.
Thankfully, help is at hand.
This is really the brains of the
Minor Planet Centre right in here.
This computer system has information
about where asteroids are,
where they will be in the future.
All the observations
all the software is in here.
We definitely need it to be running
all the time, we need it to be safe.
We need everything working here.
Do you feel a sense
of responsibility?
I definitely feel a sense of
responsibility
for keeping a track of the
asteroids. I feel like it's our duty,
it's our task to do that and I do
feel personally responsible for it.
And the task facing Tim,
is growing rapidly.
In 1999, only 10,000 asteroids
were known of.
Since then,
hundreds of thousands more,
of all shapes and sizes,
have been discovered.
Tim has developed a map to
visualise their location.
And on that map,
there's one class of asteroid
he's concerned with above all -
those near-Earth asteroids
closest to our planet.
On the screen here is a map
of the solar system.
The Sun in the centre, and the third
planet up there would the Earth.
The red dots in here are actually
near-Earth asteroids,
the green ones
are the regular main belt asteroids.
There are over 7,000 near-Earth
asteroids,
but there's one type they are
particularly concerned to locate.
Those asteroids that are
over one kilometre in diameter.
These are the monsters of the skies.
An Earth impact with one of these
would spell catastrophe
for the planet.
If a one-kilometre diameter asteroid
were to hit, say, New York City,
that would very likely affect people
in you know, 100 miles away.
It might kill people 100 miles away.
So you're talking, really,
a catastrophe, instantaneously,
as soon as it hits.
Tim's data reveals
that there are 900 asteroids
bigger than a kilometre
in those dangerous
near-Earth orbits.
But the big question -
are any of them
on a collision course with Earth?
Right now,
there's no information
that any of those large objects
will
hit the Earth in the next 100 years.
So we're safe from impacts of
those objects for at least 100 years.
But there are still smaller asteroids
than one kilometre
that we have not yet discovered.
So I can't say we're safe from them
because we don't know
where they are, just yet.
So, for now, we are safe from a
catastrophic asteroid impact.
Even if the thousands of smaller
asteroids might still pose a threat.
However another group of scientists
have a very different mystery
about asteroids to investigate.
One that may help solve
one of the greatest quandaries
about life on Earth.
This is Maunu Kea
in Hawaii. It is home
to some of the most
powerful telescopes in the world.
For 30 years, Professor Dave Jewitt
has used them to probe deep
into the solar system.
And once Dave
interrogates deep space,
it's rarely ever the same again.
In 1992,
I discovered the first objects
found beyond Neptune
since Pluto.
The biggest discovery
in the solar system
since
the discovery of the asteroids.
It was a discovery that led to Pluto
losing its status as a planet,
something the world had taken
for granted for over 60 years.
It established Dave's reputation
as a pioneering astronomer.
It's important not to work on things
that other people are working on.
All you'll do is get the same result
as everybody else. You won't make
any discoveries, you'll just
confirm what is already known.
Dave's desire to journey
where others fear to tread
has led him to this.
This bright dot with a long
hazy tail is called Elst-Pizarro.
It was found alongside all the other
asteroids in the asteroid belt.
The problem was, it just
didn't look like an asteroid.
So why did it seem so out of place?
it didn't look like the other
asteroids so it was a freak.
And it got a lot of attention
straightaway,
because it was
such a remarkable object.
Nobody had seen
anything like that before.
What had got them excited
was that to astronomers,
asteroids normally look like this.
Just a point of light.
No dust cloud,
and definitely no tail.
For years Elst-Pizarro,
with its orbit of an asteroid
but strange fuzzy appearance,
left scientists baffled.
Until finally,
someone suggested an explanation.
Finally, a paper came out saying
it must be due to the
collision between two asteroids.
So two asteroids
slammed into each other
with high speed, and shattered
and produced a cloud of dust.
So the strange tail was thought
to be the debris from a collision
between Elst-Pizarro
and another asteroid.
And, very quickly,
most of the scientific world
forgot about Elst-Pizarro.
But Dave didn't.
He had a hunch that there was more
to this puzzling little light
in the sky than at first appeared.
A hunch that, if proved correct,
might help solve one of the great
mysteries of life here on Earth.
Dave decided to investigate,
and began looking for
someone to work with.
Somebody with a head
for the challenge.
When Dave suggested that
I look at this object, I didn't
actually know anything about it.
Nothing had really been said about it
in the last 6 years since
it's been discovered,
so I just decided, OK, it's just an
interesting thing to take a look at.
Dave and Henry knew that if
Elst-Pizarro's fuzzy tail really
had been caused by a collision
the debris should
have dispersed by now,
and Elst-Pizarro should look
like a normal asteroid again.
But when they looked again,
what they saw was that
the tail was still there.
It was strong evidence
the collision theory was wrong.
Collisions are very, very rare.
Either Elst-Pizarro is
the unluckiest asteroid in the solar
system, that keeps getting whacked
and producing dust in that way,
which doesn't make any sense,
or there's another mechanism
for producing the dust.
Elst-Pizarro's appearance
remained an anomaly.
Dave and Henry realised
that if they were going to make
any real sense of it
they needed to find
another example of an asteroid
behaving in the same strange way.
Dave and Henry's problem
was that, in the 200 years
since asteroids were discovered,
Elst-Pizarro
was the only one like it.
Finding another one could be
a complete wild goose chase.
Using the giant telescopes on
Mauna Kea, Dave and Henry began to
hunt through the asteroid belt.
For four years, they
scanned the skies.
They studied 300 more asteroids.
All of them looked identical...
..except for one.
When we saw these images, I didn't
know what to think actually.
Maybe this is what we've been
looking for all this time.
But we were maybe just a bit nervous.
You know, we may be on the...
the cusp of something big.
What they'd seen was an asteroid
sporting a tiny, faint
fan-shaped tail.
Just like with Elst-Pizarro, they
were convinced it was impossible
this tail was created by
a collision between asteroids.
They had another explanation
that to many seemed unthinkable.
This is an image of a comet.
They are objects that are thought
to have been born
in the freezing
outer reaches of the solar system.
They have long, elliptical orbits
that bring them towards
the sun and the Earth.
And in comets
the tail is a sign of something
very special inside the centre.
Ice.
Their appearance is due to
the vaporisation of the ice, that
blows material off to make a tail.
So they have this distinctive
appearance, basically of having
a long tail of dust.
For 200 years
the asteroid belt was thought to be
an orbiting collection of dry
lumps of rock and metal.
Dave and Henry's new idea was that
those asteroids they had observed
might look fuzzy
and have tails because they too
actually had ice inside them.
It was a radical suggestion, because
scientists had always thought
asteroid orbits were far too close
to the sun for them to be icy.
People were uncomfortable,
because of this prevailing idea
that the asteroids are rocky,
and the comets are icy, and there
should be nothing in-between.
The reason why ice
in the asteroids mattered so much
is that it could help explain
something that makes our planet
unique in the solar system.
Our beautiful blue planet
is the only one to have
an abundant supply of liquid water.
Around 70% of the Earth's surface
is covered by the oceans.
But there has always been a mystery
as to where all this water
actually came from.
For a decade, Dave Jewitt has
been investigating this problem,
because scientists have established
that when Earth formed,
over 4.5 billion years ago,
it used to be a very different
kind of place.
The early Earth was really hot.
It formed from hot material
in orbit around the sun.
So hot that we think the entire
surface of the Earth
was covered by liquid lava for
the first 100 million years,
a bit like
the land that we see behind us.
Dave believes
the searing heat of molten rock
would have had a profound effect
on the Earth's early climate.
Because it was so hot, we also think
the early Earth was very dry.
It's like putting something in the
oven and baking it for too long.
It comes out bone dry. We think the
Earth was bone dry when it formed.
That would means that the lush, wet
climate that we enjoy today
must be the result of some
dramatic events long after
the Earth was born.
The Earth got its water some time
after it had formed and cooled down,
by being hit by objects that
carried water from somewhere
else in the solar system.
If Dave and Henry were right,
a constant stream of icy
asteroids hitting the early Earth
could have played a vital role
in bringing our planet its water.
But for all their observations,
they hadn't actually seen ice
on an asteroid.
So the one problem with our
observations is that they only
told us what the object looked like
and with that information we knew...
we thought we could only explain it
with the presence of ice
but we couldn't actually prove that
that was the case.
The last piece of the jigsaw
finally arrived early this year,
with help from the mighty
telescopes of Maunu Kea.
Andy Rivkin
makes the invisible visible,
by using a NASA telescope to look
at objects using infrared light.
The infrared part of the spectrum
is useful
because it contains
information about the composition of
asteroids and other objects,
and so by observing there you get
a better handle on the composition
than you would
if you observed only in the visible.
Andy studies the shape of
the infrared spectrum reflected off
the surface of asteroids,
because tiny differences
in the peaks and troughs can reveal
what the surface is made of.
Andy became interested
in an asteroid called 24 Themis.
The shape of its spectrum
meant something very odd must
be happening at its surface.
We started by comparing it to other
materials and objects that
we thought might be similar.
We tried comparing it to other
asteroids, but it didn't look like
any of the other asteroids.
We tried comparing it to meteorites,
and it didn't look like
any other meteorites.
So we knew we had to come up with
some other explanation.
Finally, in April this year,
Andy and his team
published their explanation
as to why 24 Themis gives off
such a strange kind of light.
We found that water ice was
actually the best choice, and
that was really exciting, because
it was the first time, certainly that
we knew of, that anyone had found
water ice out in the asteroid belt.
Even though it had been
suspected for some time
that it could be out there,
no-one had ever seen it.
Andy had finally proved
an asteroid really could be icy.
It now seems certain
the strange behaviour and tails
seen by Dave and Henry on their
asteroids was caused by ice too.
DAVE: I think any time you make
a discovery it's exciting.
Any time you find a new thing,
it's a big thrill.
Definitely a big thrill, yeah.
Cos it's hard.
It means that asteroids
could have played
one of the most important roles
in creating the Earth we see today.
We know that asteroids did hit
the Earth, for billions of years.
The question is what the asteroids
brought with them.
We previously thought
mostly rock and metal.
Now we understand that the asteroids
would also have brought
a lot more water and ice than we'd
previously suspected.
These discoveries are starting
to change our understanding
of the solar system.
Water and ice really are abundant
in the asteroid belt.
And that maybe water and ice
is more abundant throughout
the entire inner solar system.
Finding the water in the asteroid
belt is the key to starting to change
our thinking about where
Earth's water may have come from.
Astronomers still don't know
how much of Earth's water
came from asteroids
and how much from other
sources of ice such as comets.
Without that water, of course,
life on Earth could not exist.
Which provokes what is perhaps
the most intriguing question of all.
Did asteroids play a role
in the creation of life?
Not far from San Francisco,
California,
there are scientists
pondering this very question.
Scott Sandford wants to investigate
whether the basic chemicals of life
could have been formed in space,
perhaps even on an asteroid.
So he's created the conditions
of deep space in a machine.
This machine has been developed
to allow us to simulate
environmentsthat are out in space,
either in the interstellar medium,
events where stars form,
or the environments, let's say,
in the icy satellites of planets
in the outer solar system.
Environments that
have low temperatures, no air,
so vacuum, and high radiation fields.
He wants to see if the complex
carbon molecules that are essential
to life
could be created from the much
simpler chemicals found in space.
In this chamber is a sample probe
covered in a tiny layer of water,
methanol and pyrimidine
that is frozen to just 20 degrees
above absolute zero, and exposed to
intense ultraviolet light.
In this particular experiment we're
looking at whether certain conditions
will form one of the nucleobases,
so one of the molecules
that makes up our DNA.
And from his analysis of samples
from experiments like this,
Scott has made
a remarkable discovery.
By processing ices of the type
we see out in space, we can make
some of the building blocks that
we see in biology on the Earth today.
We're making the building blocks
of life, that's what we're finding.
Just because you can create these
building blocks of life in a lab,
it doesn't mean it really happens
on an asteroid.
So Scott has carefully examined
meteorite samples to see if they
contain traces of these chemicals.
In some classes
of meteorites, which we think
come from asteroids, we find a
variety of organic compounds.
And these include things that
some people are familiar with,
like amino acids, the building
blocks of proteins in our bodies,
but also materials
like the nucleobases,
the building blocks of DNA.
So hidden within the rock
could have been the materials
that made possible
the emergence of life on Earth.
And that means that when asteroids
struck Earth billions of years ago
they could have completely
transformed our planet.
Asteroids could have played
an important role in getting
life started on Earth
by delivering the raw starting
materials that we need to get
everything going to get life started.
It seems the story of life on Earth
is inextricably linked
to the story...
of asteroids.
The possibility that asteroids
hold the key to some of the deepest
mysteries about our planet explains
why scientists have always dreamt of
reaching out into space and bringing
back a pristine asteroid sample.
And earlier this year, that
wish may finally have come true.
In June, one of the strangest space
missions in history came to an end.
It might look like a
firework display, but this
is actually a Japanese spacecraft
re-entering the Earth's atmosphere.
Seven years after it first left
the Earth, the Hayabusa probe
landed in the Australian desert.
The scientific team were
careful to handle the crashed
probe with extreme caution.
Because within this small container
is what scientists hope will be the
first ever asteroid sample
collected directly from space.
The sample consists a lot of little
grains, and some of the grains
are as small as ten microns,
so ten millionths of a metre across,
so this is a particle smaller
than the width of a human hair.
Even in a microscope it looks
like a dot, OK, and so, um,
the analyses of such small samples
is obviously complicated.
Obviously our hope is that some
of that material really is from
the asteroid,
but at this point we don't
know for sure one way or the other.
It may be months or even years,
before the team discovers what
if anything these grains can reveal.
While many scientists
are excited about what
asteroids might tell us about
the beginnings of life on Earth,
new research suggests that it is how
asteroids might put an end to life
that should really concern us.
On the 6th of October 2008
asteroid hunter Richard Kowalski
saw something that would
help change the assessment
of the threat presented by
asteroid impacts.
The night was proceeding
normally and up on the screen
came another asteroid.
As I continued to make observations
throughout the night it appeared
to be moving slightly faster.
And this indicates that the
object is close to the Earth.
As with any other asteroid,
Richard reported what he'd found
to the Minor Planet Center.
I got up in the morning,
about 7 o'clock.
I had a message from the computer
saying, "could not compute
an orbit for a particular object".
I grabbed the observations of
this object and I computed an orbit
and it was immediately apparent,
right then, that that object
was going to hit the Earth.
and sort of ominous fashion,
it said it was in 19 hours.
Following a strict written protocol,
Tim quickly reported the findings
to NASA's asteroid
investigation team in California.
We got a call from Tim Spahr
at the Minor Planet Center
saying we had an
impacter coming in, in less than
24 hours.
So that woke me up.
NASA's expert on asteroid orbits,
Steve Chesley, immediately
started to verify the data.
Steve The first thing I saw
was a 1.000,
100% probability of impact
and erm, in less than a days' time.
This I'd never seen,
anything like this outside of
simulations and software testing.
An asteroid strike
would create a huge explosion.
NASA feared this might be mistaken
for a nuclear bomb.
We wanted folks to know that this
was a natural event by mother nature
rather than some sort of a
man-made event like a missile
or something dreadful.
Information passed rapidly
up the chain of command.
So, NASA headquarters
notified the Whitehouse
that this was coming.
Everyone wanted to know
where it would strike
NASA predicted a remote
area of the Nubian desert.
AT quarter to three in the morning,
NASA were proved right.
The explosion created a vast
fireball burning as hot as the sun.
It was so big and so hot, this image
was captured by a weather satellite.
As dawn broke,
the smoke trail it left behind was
still visible from the ground.
I definitely think
the impact was a wake-up call.
I have to admit I never thought I'd
see that in my career, where we would
discover something that would
hit the Earth later that day.
What makes this impact so worrying
is that this asteroid was too small
for anyone to see until it was
very, very close to the Earth
For one scientist, it's was
a salutary reminder that
we cannot afford to ignore the
threat posed by small asteroids.
Physicist Mark Boslough uses
one of the world's most powerful
supercomputers to study the hazards
facing our planet, from climate
change to nuclear explosions.
But for years, he's been fascinated
by a strange event at the
beginning of the last century,
and what it might tell us about
the threat of asteroid impacts.
On June 30th 1908, without warning,
a massive explosion wiped out
over 1,500 square kilometres
of Siberian forest.
Millions of trees were destroyed.
Scientists thought it had been
caused by an asteroid strike.
But then why was there no sign
of any kind of impact crater?
The answer is that the devastation
had to be caused by an asteroid
attack of a very particular kind.
The explosion was caused by an
asteroid that entered the atmosphere,
got close to the surface and
exploded before it hit the ground.
That explosion created a blast wave
with hurricane-force winds
that knocked trees over
for thousands of square miles.
Scientists call it an air burst - a
massive explosion in the atmosphere
rather than on the ground.
As it enters the atmosphere
at speeds of up to
20 kilometres per second
the air resistance decelerates the
asteroid so fast it breaks
apart in a huge explosion.
And crucially,
it is small asteroids that are most
likely to explode in this way.
Most of the damage from an explosion
like this is actually the blast
waves, it's the very high winds.
Based on the physics
of nuclear explosions,
the original air burst model
estimates the Tunguska explosion
must have been 1,000 times bigger
than the nuclear bombs
at Hiroshima and Nagasaki.
But crucially,
the air burst model suggests the
asteroid would have packed this huge
destructive force
even though it was as small
as 100 metres in diameter.
But Mark realised there
was another problem.
The model was ignoring a crucial
difference between nuclear bomb
air bursts, and asteroids.
Asteroids are extremely heavy
and move so fast that
they carry huge momentum
He created a new simulation to
investigate the effect this would
have on their destructive power.
In this simulation I include more of
the physics to be more realistic,
you can see that the main shockwave
doesn't come out of the point of the
explosion, but it comes out from the
point where the fireball descends to.
so by the time the shockwave hit
the ground it's much stronger
than it would otherwise be so
there is more damage on the ground,
because the destructive
power was carried downward.
Based on Mark's new calculations,
the devastation at Tunguska
could have been caused
by an asteroid only one third as
large as previous estimates.
Perhaps as small as 30-50
metres in diameter.
And for him this carries
a worrying implication.
Smaller asteroids are more
dangerous than we used to think
and because there are so many
more smaller asteroids than bigger
asteroids we need to take that risk
more seriously than we used to.
Mark's work means scientists
may have to redraw the
asteroid threat map.
If a Tunguska scale asteroid
exploded over London or New York it
would be very destructive, it would
be as destructive as a nuclear bomb
exploding over one of those cities.
Scientists estimate that there
could be over a million of these
kinds of asteroids up in space.
But nobody knows where they are,
or where they are headed.
A 2010 report by the American
National Academies of Sciences,
was so concerned
about the potential threat
to Earth from the smallest kind of
asteroids, that it has called for
a new survey to track them down.
The problems is that even for
dedicated asteroid hunters like
Richard Kowalski,
they are extremely hard to find.
Many of them are as dark as a
charcoal briquette and we see
them by reflected sunlight.
So you can imagine a 100-metre
charcoal briquette out in space
is going to be kind of hard to see.
And that means that if an asteroid
like this is heading for Earth,
we might only see it when it is very
close, with very little warning.
There's a reasonable chance that
you'll see it for the first time, on
it's terminal trajectory, just
days, or weeks, before the impact.
If that were to happen,
there is nothing that anyone could
to stop it from hitting the Earth.
For the public authorities, the
only option, would be to try to get
the thousands or even millions
of people out of the impact zone.
I think Katrina, Hurricane Katrina,
really illustrated how hard it
is to evacuate a large area.
It's not set up that we have an
asteroid evacuation plan
in place right now.
I know it's been discussed at the UN,
but if we were to be
issued 3 days' warning, I really
don't know what would happen.
And it wouldn't be very good.
I'm sure we're not
ready for that yet.
However far away they may be,
and however difficult to find,
scientists now understand that
Earth's past
and its future cannot be separated
from these tiny rocks of destiny.
The quest to understand them will
continue on Earth and from space.
NASA currently has a spacecraft
en route to visit two
of the largest asteroids
in the solar system.
It will arrive in July 2011.
And President Obama has challenged
NASA to send astronauts to an
asteroid by 2025.
200 years after
they were first discovered,
solar system science has finally
entered the age of the asteroids.
The good, the bad and the ugly.
Are asteroids bad, good or ugly?
I'd say all of the above.
I wouldn't say that asteroids
are good or bad.
They essentially created the solar
system we live in
and the planet that we live on.
They've shaped the Earth in ways,
it's safe to say,
humans wouldn't be around
but for the asteroid impact.
I take asteroids like people -
I take them as I find them
and try to learn their
individual foibles.
I think ultimately asteroids will be
our friends
because they have the capability
of giving us resources for use
as we try to explore
and extend our reach into space.
Asteroids are certainly not ugly.
Asteroids are beautiful.
The ones that we don't understand, I
think that makes them more beautiful.
That's the beauty of science.
That's why we keep doing it.
It's to try to learn more things and
when we get a curve ball thrown in,
that's part of the process.
That's the fun.
I have an asteroid named after
myself. It's (2956) Yeomans.
That's quite a hoot.
I do have an asteroid
and this is it.
(17857) Hsieh 1998KR1
I have an asteroid. It's called
(6434) Jewitt. It makes me feel like
I'm part of the cosmos.
I have an asteroid named after me.
Pete Schulz. It looks like I've got
a bullet with my name on it.
HE LAUGHS