Original subtitles

- From the beginnings of our solar system

four and a half billion years ago,

there remained tantalizing clues

to it's evolution,

remnant debris, asteroids, and comets.

They vary in size from grains of dust

to mountain sides,

from footballs to planetoids.

They were the building blocks of the planets

and perhaps carried the origins of life itself.

Now within our grasp,

these rocks of ice and dust

are ready to give up their secrets.

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Asteroids are believed to be made of chondrules,

flash-heated grains of rock

within the stellar disk of our forming solar system.

These chondrules clustered together

forming the first asteroids

and the building blocks of the planets.

Once the solar system had evolved,

there was a lot of asteroid material left over.

They covered a broad spectrum of types.

The largest of these are minor planets,

or planetoids, large enough

to have an ovoid shape.

This category took the previous planet Pluto

off the major list and on to the minor.

The smallest remnants of debris

are often called meteroids.

There are, in fact, several minor planets.

Some have been succonded into

planetary orbit and have become moons.

The traditional asteroid belt

between Mars and Jupiter

has one called Ceres,

the largest and the first to be detected.

Our first closeup of an asteroid

was courtesy of Galileo

on it's flight through the main

asteroid belt towards Jupiter.

It photographed 951 Gaspra,

an S-type asteroid with an average diameter

of just over six kilometers.

The S stands for stony composition.

Galileo then photographed the larger

243 Ida at 15 and a half kilometers wide,

revealing that it has it's own moon

named Dactyl.

Asteroids are not limited to the asteroid belt

between the orbits of Mars and Jupiter.

Many orbit much closer to Earth

and are known as near-Earth objects,

or NEOs.

- Radar is a very powerful instrument

that we use to study near-Earth asteroids.

Astro Tutatis was millions of kilometers away

and we were were able to resolve surface rocks.

We could see boulders.

- There are currently only two

radar facilities in the world

that have sufficient sensitivity

for doing regular observations

of near-Earth objects,

Arecibo and Goldstone.

- Even the most powerful optical telescopes,

and I'm talking even Hubble Telescope,

they can only see this asteroid

as a point of light.

It is just too far and too small.

- It provides an extraordinary opportunity

to get very detailed radar images.

- You are transmitting microwaves,

it's propagating at the speed of light

toward the asteroid,

it is bouncing back,

and this radar echo is containing

surface features of the asteroid,

it's telling us about it's rotation,

and it's very precisely pinpointing

it's distance from the radar.

- These asteroids were imaged with

ground-based radar.

BL86 revealed it has it's own moon

and asteroid HQ124

passed very close to Earth,

some three and a quarter times

the distance to the moon.

It is due to return sometime

in the 24th Century.

Scientists are looking much more

closely at these objects

for their potential to pass through

Earth's orbital plane

and perhaps pose a threat.

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The most common type of asteroid

is the C-type, carbonaceous,

accounting for about 75% of known asteroids.

The probe NEAR Shoemaker

was the first dedicated asteroid probe

launched by NASA.

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It photographed 253 Mathilde, a C-type,

then moved on to 433 Eros,

the largest visited at the time,

where it orbited, took extensive measurements,

and, more by accident than good planning,

landed on the asteroid,

the first probe to do so.

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Deep Space 1, an experimental NASA probe,

was sent to investigate an asteroid,

9969 Braille.

Technical errors returned poor imagery,

however the probe continued on

to it's second rendezvous

for the first time with a comet,

19P/Borrelly.

Comets are closely related to asteroids

but originate from the cold, dark

outer boundaries of our solar system.

- Comets are bodies in our solar system

that have been left over

ever since the solar system formed

some 4.5 billion years ago,

and therefore, when we look into comets,

we look into the past of our solar system.

And so by investigating the details of comets,

how they formed, how they evolved,

we can actually have a glimpse into

how our solar system formed

and, in the end, how the Earth formed

and why we are here.

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Comets have been recorded throughout history

as they are easily observed

when close to the Sun,

often considered an omen.

One comet of note

was Halley's.

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In 1986, Halley's Comet returned once again,

and this time it was met with a

veritable armada of space probes.

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The first attempt at a space rendezvous

was with the International Comet Explorer,

or ICE.

It passed through the tail of

Comet 21P/Giacobini-Zinner

on it's way to meet Halley.

The European Space Agency sent Giotto,

the Russian and French sent two probes

via Venus, Vega 1 and Vega 2.

Japan sent Suisei and Sakigake,

that country's first deep-space probes.

Their measurements went on to refine

the targeting for Giotto

to make a much closer pass

of the comet's nucleus than first planned.

In 1994, astronomers and scientists

were given an unexpected treat.

Comet Shoemaker-Levy broke apart

and struck Jupiter

in a spectacularly violent fashion.

Comets required more study.

The Stardust probe was dispatched

to investigate 5535 Annefrank,

Wild 2, and then the Tempel 1 comet.

It returned a sample of cometary tail to Earth.

- Our biggest discovery that we did

was looking at this cometary material

that was returned from NASA's Stardust mission.

The Stardust mission went up,

rendezvoused with the comet,

brought back very small amounts of material,

comet material and comet exposed material.

We had basically one shot at looking at this

and it was really pushing our limits of detection.

So I spent about two years

optimizing our technique,

really rehearsing, practicing,

getting everything as perfect as possible

before the one day of doing measurements,

it's sort of all leading up to one big game,

one big day.

And also, just working with meteorites

and working with the cometary material,

I'm working with something that's

four and a half billion years old

that very few people ever get to play with.

The two days of being able to do

the actual measurements

make up for all of the rehearsals that it takes.

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- JAXA launched Hayabusa

to study asteroid 25143 Itokawa

and to retrieve a sample from the surface

in a touch-and-go maneuver.

The mission took a total of

seven years to accomplish,

with the sample-return pod

retrieved from the Australian Outback

in 2010.

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(rockets burning)

Launched a year earlier

by the European Space Agency,

was a very ambitious spacecraft

called Rosetta.

It's goal: to land a probe on comet,

67P/Churyumov-Gerasimenko.

Just getting there was to prove

a challenge in astro-navigation.

- Well when you want to rendezvous with a comet,

you have to accelerate the spacecraft

and match the same velocity

that the comet has around the Sun.

So this is the problem,

not only the distance but also the velocity.

There is no rocket that can give us

the velocity needed to be

as fast as the comet.

I close to a planet

and you use the gravitational attraction

of the planet to actually

accelerate your spacecraft.

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- It passed by asteroids 2867 Steins

and 21 Lutetia.

- Lutetia is a very strange target,

a very strange asteroid.

We believe that it may be a

C-class asteroid which means that

it is very primitive.

However, it shows from ground-based

and also spaceborne observations

that Lutetia does not look

completely like a C-type asteroid

and we are really puzzled about

what it really may be.

- The spacecraft then moved on

to its primary target, Comet 67P.

- The nucleus is

pulling the spacecraft out of its planned orbit,

and that can be seen as a

shift in frequency of the transmitted

radio signal from the spacecraft,

and the extent of this frequency shift

is a measure of the mass of the comet nucleus,

so we are able to weigh the nucleus here.

- There is no ice at the top,

so it's covered by a mantle

that we consider is essentially

made of organic material,

that's why it's very dark,

and this material is one of the key things

we would like to explore and analyze.

- These organics may hold the secret

to life on Earth.

- What it's all about is the carbon chemistry,

how much did the comets bring to Earth.

So was it just the right elements,

the right building blocks,

or was there more information in it

when these comets already arrived?

- To try and answer these questions,

ESA attempted one of the most daring missions

mankind has ever undertaken:

to land a probe on the surface of the comet.

(fast-paced symphonic rock music)

Landing on a comet

is one of the hardest things

that has ever been done

by the human species.

- This is the comet.

It's roughly a one in thousand model,

so the real thing is thousand times bigger.

The landing site is roughly here,

which we are aiming for

to the deliver the lander,

it's the flattest part we could find.

What we are studying at the comet

with the instruments

are basically, what are the ingredients,

which materials are present,

and coming back to the wonky

objectives of the mission,

how complex are the materials

present at the comet.

- Landing means

flying very, very slowly over the comet

and then gently pushing away the lander.

It's not a landing like you can imagine

on the moon,

where you come with rockets

and you have to break.

Here the problem is the opposite.

You have to really touch gently the comet,

the forces involved are very small.

- If I get meaningful data,

that would be just marvelous.

If the descent works, the landing is okay,

we receive a sample,

and the whole thing runs smoothly,

that would be just great,

(chuckles)

but we need a lot of luck, really.

We had a lot of luck already.

(crowd cheering and applauding)

So we are sitting on the surface,

Philae is talking to us,

more data to come

and to be on our way (cheering drowns out speaker).

Going down, which you should do,

of course, we are there (mumbles) job,

we are on the comet.

- The science has started now.

We have the first results

that give us the first comprehension

of what we think the comet is,

where it started from.

Now for the rest of the year,

we'll watch how the comet evolves,

we'll unlock how the comet works.

We're looking at where

the gas and the dust start to

accelerate from the surface

and how that beginning of the coma,

that birth of the coma, works,

so how the coma develops as

it goes to higher altitudes.

This region has only ever been

theoretically constrained or modeled.

These will be the first measurements

we make in this area, or this region,

and that's a really big, important target for us.

- Eventually, the tiny probe shuts down.

- Having Philae reactivated

is not so likely but is not impossible.

Philae was designed to hibernate,

was designed to switch off

and be able to reactivate itself.

Of course, we expected this to be

a duration of few days or a few weeks,

not a few months,

but okay.

We will see, maybe we are lucky

and the UNICEF survived these months

and will reactivate in June, July.

- While observing the asteroids,

scientists were surprised to find one

with what looked like a cometary tail.

After careful study,

scientists realized they observing

the results of the impact of two asteroids.

596 Scheila has been struck at high speed

by a small asteroid.

The impact hit with the force of

a 100 kiloton nuclear bomb.

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NASA had done something similar

with Deep Impact,

a probe sent to Comet Tempel 1,

where it dispatched a kinetic impactor

which struck the comet

to study the impact and the debris

thrown up as a consequence.

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Soon after, NASA launched

another ion-powered probe, Dawn,

which also had an extraordinary mission:

to travel deep into the asteroid belt

between Mars and Jupiter.

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It's targets: two of the largest asteroids

in the solar system.

Dawn rendezvoused with 4 Vesta

and orbited it for over a year,

returning a wealth of data.

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Dawn then departed and cruised toward Ceres,

the largest of the asteroids,

a planetoid, where it has obtained orbit,

and begun its study.

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JAXA, the Japanese space agency,

has recently launched a second Hayabusa probe,

this one with many improvements over the first.

Its target is the C-type asteroid,

1999 JU3.

It's expected to reach its destination

in three years, collect samples,

and return to Earth by 2020.

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NASA has announced the

OSIRIS-REx sample-return mission

to asteroid 1999 RQ36,

better known as Bennu.

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It's expected to launch sometime

in the near future,

and after a two-year journey,

orbit and map the surface

before touching down to retrieve

two kilograms of material.

The probe sample's return

is expected in 2023.

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There is also a practical reason

to study asteroids.

In 2013, an asteroid

with a mass of about 9,100 tons

exploded over Chelyabinsk, Russia

with the force of 20 Hiroshima bombs,

causing 1,500 injuries

and damaging 7,000 buildings.

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It isn't the first asteroid strike on Earth

as the dinosaurs can attest to,

and probably not the last.

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Through the United Nations,

ESA and other major space agencies

have established a safeguard program.

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- The new NEOWISE data

have returned two very important findings.

First, we've been able to determine

that we found 93% of all the

near-Earth asteroids that are out there

that are larger than one kilometer.

We've also been able to tell that

there somewhat fewer near-Earth asteroids

that are larger than 100 meters

than were previously thought.

However, fewer does not mean none.

That leaves about 15,000 asteroids

larger than 100 meters that remain to be found.

- This advisory group is also planning

intervention missions if needed.

- We think that we can cope with

deflecting an asteroid

with two different technologies, mainly.

One is what we call kinetic impactor,

hitting the asteroid and pushing it out of the way.

The second one is take a heavy spacecraft

and use it as a gravity tractor,

so by the mass of the spacecraft

you pull the asteroid away.

- There is one project in the planning stage

to snag a small asteroid in the near-Earth region

and drag it into a lunar orbit.

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There, it can be met by astronauts

aboard an Orion capsule,

who will study the asteroid first hand,

take extensive samples,

and return to Earth.

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For the more we know,

the better prepared we are

to take our place in the solar system.

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