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Lift off of Messenger on Nasa's
mission to Mercury.
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# They'll say
no-one can see us
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00:00:16,040 --> 00:00:23,720
# That we're estranged
and all alone
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00:00:23,720 --> 00:00:30,800
# They believe
nothing can reach us
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00:00:30,800 --> 00:00:38,080
# And pull us out of
the boundless gloom
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# They're wrong
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# They're wrong
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# They're wrong. #
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Beyond the inner solar system...
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..past the asteroid belt...
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..lies Jupiter.
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00:01:17,320 --> 00:01:21,480
The largest of the planets
is a giant swirling ball of gas...
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..its marbled appearance generated
by violent winds
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00:01:29,400 --> 00:01:31,600
that rage through its clouds.
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00:01:41,320 --> 00:01:45,320
Jupiter is a world as strange
as it is remote.
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If you fly upwards, only about
100km or so,
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you reach the edge of our atmosphere
and the blackness of space.
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It's really not that far.
19
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But once you're in space,
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the distance scales are sort of
incomprehensible.
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00:02:05,320 --> 00:02:09,320
I mean, Venus, the closest planet,
is over 40 million kilometres away.
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Jupiter around 650 million
kilometres.
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It takes our fastest spacecraft
years to get there.
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00:02:16,760 --> 00:02:21,400
So, the idea that those planets
could have any influence on us
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here on Earth seems fanciful.
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And, indeed, if you're talking about
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your chances of meeting a handsome
stranger
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or your life plans requiring a
moderate reconfiguration
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about a week on Wednesday,
then you would be right.
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00:02:35,600 --> 00:02:40,480
However, if you ask more profound
questions, deeper questions like,
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"Why is the Earth the way that
it is?
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00:02:42,840 --> 00:02:44,760
"Why is there life on Earth?
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"Why do we exist at all?"
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00:02:47,120 --> 00:02:50,640
then it turns out that the planets,
and Jupiter in particular,
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have had a profound effect.
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THUNDER
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00:03:09,400 --> 00:03:13,440
Early in its life, the young
Jupiter went on the rampage.
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00:03:21,400 --> 00:03:24,920
The giant planet embarked
on a voyage of destruction
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00:03:24,920 --> 00:03:26,680
across the solar system...
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..that transformed the destiny
of the planets,
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and the course of life on Earth.
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Jupiter is the godfather
of the planets.
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Understand it and you understand
how the solar system came to be.
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On Earth, we can see glimpses
of Jupiter's power...
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..in the scars it's left...
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..on the face of the planet.
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This is the famous Barringer
Meteor Crater in Arizona.
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It is about a kilometre across,
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170 metres from the rim to the
crater floor
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and it was created about 50,000
years ago
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when a meteorite, 50 metres across,
entered the Earth's atmosphere
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travelling at about 13km per
second.
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00:05:00,040 --> 00:05:02,480
That means it would have taken
around, what, seven seconds
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to go from the top of the atmosphere
to the ground
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and it hit with such force that the
energy released
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was equivalent to ten megatons of
TNT.
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And that is a very large
nuclear bomb.
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00:05:19,960 --> 00:05:22,120
The meteorite that hit the Earth
here
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is thought to have come from the
asteroid belt...
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..the ring of rocky debris
that orbits at the edge
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of the inner solar system.
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And it was deflected from its orbit
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most likely by the gravitational
influence of Jupiter.
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Jupiter is a completely different
class of planet to the Earth.
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A gas giant.
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A swirling ball of hydrogen
and helium so large
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you could fit 1,300 Earths inside.
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Jupiter can exert such a powerful
influence on the asteroids
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because it's so massive.
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It's about two-and-a-half times
the mass of all the other planets,
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moons and asteroids in the solar
system combined.
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And, therefore, it has a strong
gravitational pull.
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00:06:30,120 --> 00:06:33,280
And this means that Jupiter
exerts an influence
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across the entire solar system
that's second only to the sun.
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And that influenced us far
more than create the odd crater.
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It can change the history
of worlds.
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To understand how Jupiter rose
to such dominance,
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you have to go back to a time before
the solar system even existed.
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Nearly five billion years ago,
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a distant exploding star sent
a shock wave across the galaxy...
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..causing the cloud of gas and dust
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that would become our solar system
to collapse...
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..as the sun began to form.
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But further out, something
else was growing.
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After 50 million years...
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..the sun's nuclear furnace ignited.
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The light of its first dawn...
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..revealing Jupiter...
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..the solar system's first world.
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A planet born so early, it swept
up most of the material
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left over from the formation of
the sun.
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Because of its dominance, Jupiter
had a profound effect
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on the newly forming solar system
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and paved the way for our living
world to form.
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This is a model of our solar system.
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{\an8}So, here's the sun, and then we have
the four inner rocky planets,
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{\an8}Mercury, Venus, Earth and Mars.
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Then comes the asteroid belt,
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the ring of millions of smaller
pieces of rock
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orbiting around the sun.
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And then the gas giants.
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Jupiter, Saturn, Uranus and Neptune.
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Now, this has a pleasing regular
structure about it.
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All the rocky planets close to the
star
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and the gas giants further out.
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And we thought that this must be the
natural order of things,
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the way that solar systems
have to form,
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until we started to detect planets
around distant stars
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and then we found that this
arrangement is not typical at all.
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Our sun is just one of around
300 billion stars in our galaxy...
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..and almost every one of those
stars
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is home to its own system of
planets.
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In most other systems, the region
where our planet orbits is empty.
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Instead, closer to the star, we see
super-Earths,
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vast rocky planets
many times bigger than our own.
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But, crucially, these worlds are
thought
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to have thick toxic
atmospheres,
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making them completely inhospitable
to life.
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And that raises a very interesting
question.
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Why, then, is our solar system
the way that it is?
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00:11:08,040 --> 00:11:09,520
To answer that question,
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we've sent spacecraft to every one
of the planets...
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00:11:15,360 --> 00:11:17,800
..and they've uncovered strange
anomalies
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that reveal our solar system's past.
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00:11:23,520 --> 00:11:27,400
Our missions to Venus found
that it once had far more water
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than you'd expect for a planet
so close to the sun...
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..just as Earth does today.
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00:11:39,520 --> 00:11:41,720
The spacecraft we've sent to Mars
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touched down on a world that is
curiously just half the size
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of her sister planets
Earth and Venus.
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And in the asteroid belt,
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we've uncovered a graveyard
of failed worlds...
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..their growth mysteriously
cut short.
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00:12:14,800 --> 00:12:17,040
To cause all these anomalies,
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00:12:17,040 --> 00:12:20,640
it's thought that something
catastrophic must have happened
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very early in the solar system's
history.
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00:12:26,120 --> 00:12:30,000
All the evidence suggests
that around 4.5 billion years ago,
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Jupiter's orbit began to change,
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00:12:32,040 --> 00:12:34,880
triggering a period of unprecedented
violence
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00:12:34,880 --> 00:12:39,000
which completely transformed the
face of the young solar system.
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And we know this because
the marauding planet
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left a trail of destruction
in its wake.
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Early in its life, Jupiter began
to move inwards towards the sun...
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..and the effects of that journey
can be seen to this day.
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00:13:14,240 --> 00:13:17,960
In between the orbits of Mars
and Jupiter...
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..lies the asteroid belt...
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..a desolate wasteland of debris
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left over from the beginning
of the solar system.
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Rocky bodies too small to be planets
in their own right.
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In science fiction films, the
asteroid belt is often depicted
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00:14:01,280 --> 00:14:04,520
as an un-navigable
mass of tumbling rubble.
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But it's not like that at all.
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So much so, in fact, that modern
spacecraft engineers
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can fly a spacecraft through without
making any course corrections.
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The reason for that is there's not
much mass in the asteroid belt.
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A sum total of all of them is only
about 4% the mass of the moon
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and they're spread out in a huge
sort of ring,
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out beyond the orbit of Mars.
So, it's a vast amount of space.
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That means that the average distance
between any two large asteroids
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is about eight times the distance
between the Earth and the moon.
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So, I could stand on one of those
large asteroids
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and look out into space
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and my nearest neighbour would just
be a dim star in the dark.
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But scattered amongst the rubble
are objects
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that are far more than mere rocks.
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Five, four, three,
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two, main engine start, one,
zero and lift off
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of the Delta II Rocket.
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00:15:06,800 --> 00:15:09,160
In 2007, Nasa's Dawn mission
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was sent to explore the two largest
objects in the asteroid belt.
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After a year in orbit around
the giant asteroid Vesta...
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..in March 2015...
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..Dawn made its final approach
on a body so large
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it makes up almost a third of the
mass of the entire asteroid belt...
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..Ceres.
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On arrival, the first images Dawn
sent back to Earth
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contained something entirely
unexpected...
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..mysterious bright patches in one
of Ceres' largest craters.
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Spectral analysis of the images
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showed that the patches were,
in fact,
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the salty residue left
behind by liquid water...
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..suggesting there must be large
amounts of ice
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just beneath the crust.
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00:17:17,400 --> 00:17:22,600
Dawn went on to discover over 300
bright spots all over the surface.
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And this means that beneath
its thin crust,
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00:17:30,360 --> 00:17:35,120
Ceres has a thick, ice-rich mantle
surrounding its rocky core...
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..evidence that the dwarf planet
is made up of multiple layers.
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The interior of Ceres is like
nothing else in the asteroid belt.
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The differentiation, that separation
into layers, observed by Dawn,
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is more characteristic of a planet
than an asteroid.
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00:18:10,160 --> 00:18:14,680
So, 4.5 billion years ago, Ceres
was well on its way
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00:18:14,680 --> 00:18:16,600
to becoming a fully-fledged world.
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It's thought that's in its infancy
Ceres was very different.
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The water that now lies frozen
within its interior was once liquid.
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Protected beneath a thin
layer of ice...
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..Ceres was once covered
by a deep saltwater ocean.
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00:19:13,440 --> 00:19:16,040
Before Ceres had reached
its full potential,
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00:19:16,040 --> 00:19:18,440
a great disturbance sent
shock waves through
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00:19:18,440 --> 00:19:20,800
what would one day become
the asteroid belt
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00:19:20,800 --> 00:19:22,880
and cut its development short.
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00:19:35,280 --> 00:19:37,960
As Jupiter circled the young sun,
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00:19:37,960 --> 00:19:41,080
it started to clear a path
through the gas and dust
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00:19:41,080 --> 00:19:43,080
that shrouded the early
solar system...
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..but that process caused it to do
something alarming.
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00:19:56,080 --> 00:19:59,880
Gravitational interactions with the
gas made the giant planets
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00:19:59,880 --> 00:20:01,960
spiral inwards towards the sun...
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00:20:05,320 --> 00:20:07,600
..ploughing straight through the
region of space
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00:20:07,600 --> 00:20:09,760
that would become the
asteroid belt...
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00:20:12,280 --> 00:20:14,680
..scattering the material
from which Ceres
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00:20:14,680 --> 00:20:16,280
would otherwise have grown.
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00:20:23,080 --> 00:20:25,840
Computer simulations of the early
solar system
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00:20:25,840 --> 00:20:29,320
suggest that the asteroid belt once
contained enough material
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00:20:29,320 --> 00:20:32,160
to build a planet the size of
the Earth.
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00:20:32,160 --> 00:20:35,280
And perhaps that was Ceres' destiny.
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00:20:35,280 --> 00:20:38,200
But when Jupiter passed through,
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00:20:38,200 --> 00:20:42,240
it scattered 99.9% of the material
away,
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00:20:42,240 --> 00:20:44,320
and Ceres' fate was sealed.
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00:20:50,920 --> 00:20:54,840
Within 100 million years,
Ceres' ocean froze
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00:20:54,840 --> 00:20:57,040
and was buried beneath its crust.
220
00:21:01,280 --> 00:21:04,200
The young planet's development
cut short
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00:21:04,200 --> 00:21:06,720
before it could fulfil its promise.
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00:21:19,560 --> 00:21:23,320
But Jupiter's reign of terror was
far from over.
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00:21:30,160 --> 00:21:32,200
It would continue its journey
inwards
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00:21:32,200 --> 00:21:34,800
towards the place our planet
was beginning to form...
225
00:21:37,920 --> 00:21:40,960
..threatening the very existence of
Earth.
226
00:21:46,160 --> 00:21:50,400
Jupiter had such an overwhelming
effect on the young solar system
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00:21:50,400 --> 00:21:52,920
because of its powerful
gravitational field...
228
00:22:12,400 --> 00:22:15,880
..the effects of which we can
still witness today.
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00:23:10,440 --> 00:23:13,320
Jupiter exerts its influence
across the solar system
230
00:23:13,320 --> 00:23:15,240
through its gravitational field...
231
00:23:23,960 --> 00:23:27,320
..which is by far the most powerful
of all the planets,
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00:23:27,320 --> 00:23:30,280
because Jupiter is the most massive
of all the planets.
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00:23:30,280 --> 00:23:34,280
It's about 320 times the mass
of the Earth.
234
00:23:34,280 --> 00:23:36,960
That's why it was so destructive
in the past.
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00:23:36,960 --> 00:23:40,640
And we see the power of
that gravitational field today
236
00:23:40,640 --> 00:23:45,760
in its influence on the closest
of Jupiter's largest moons, Io.
237
00:23:59,400 --> 00:24:02,680
Io is the most volcanic
world in the solar system.
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00:24:07,800 --> 00:24:11,680
Its surface covered with hundreds
of active volcanoes...
239
00:24:16,880 --> 00:24:18,760
..and lakes of molten lava.
240
00:24:25,360 --> 00:24:28,520
The largest, known as Loki Patera,
241
00:24:28,520 --> 00:24:31,760
is more than 200km in diameter.
242
00:24:40,960 --> 00:24:44,720
A million times the area
of any lava lake on Earth.
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Its surface tormented by waves
of molten rock.
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00:25:02,680 --> 00:25:04,720
Io is a vision of hell...
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00:25:10,480 --> 00:25:13,760
..created by the moon's proximity
to Jupiter.
246
00:25:32,840 --> 00:25:37,240
Volcanism here on Earth
is powered by the internal heat
247
00:25:37,240 --> 00:25:39,040
down below the surface.
248
00:25:39,040 --> 00:25:40,840
Now, much of that is residual heat
249
00:25:40,840 --> 00:25:43,120
left over from the Earth's
formation
250
00:25:43,120 --> 00:25:46,760
four-and-a-half billion years ago,
about half of it, and the other half
251
00:25:46,760 --> 00:25:51,520
is down to radioactive decay of
elements around the Earth's core.
252
00:25:51,520 --> 00:25:53,920
Now, on Io it's different.
253
00:25:54,920 --> 00:25:56,600
Io's a much smaller world
254
00:25:56,600 --> 00:25:59,920
and so it didn't retain
much residual heat.
255
00:25:59,920 --> 00:26:03,800
So, there, the volcanoes are powered
by a different process.
256
00:26:03,800 --> 00:26:05,840
It's known as tidal heating.
257
00:26:12,600 --> 00:26:15,360
The energy that drives Io's
volcanism
258
00:26:15,360 --> 00:26:18,720
doesn't come from heat
stored within the moon.
259
00:26:22,080 --> 00:26:23,800
It's generated by gravity...
260
00:26:26,760 --> 00:26:30,840
..because Io orbits just 350,000km
261
00:26:30,840 --> 00:26:33,320
from the tops of Jupiter's clouds.
262
00:26:49,720 --> 00:26:53,800
Io orbits at about the same distance
from Jupiter
263
00:26:53,800 --> 00:26:55,600
as our moon orbits the Earth.
264
00:26:55,600 --> 00:26:58,240
But because Jupiter is so much more
massive,
265
00:26:58,240 --> 00:26:59,640
Io goes around much more quickly.
266
00:26:59,640 --> 00:27:03,080
In fact, it goes around once every
42 hours.
267
00:27:03,080 --> 00:27:05,800
Now, if Io were Jupiter's only moon,
268
00:27:05,800 --> 00:27:07,960
that orbit would be circular,
269
00:27:07,960 --> 00:27:09,240
but it isn't.
270
00:27:13,040 --> 00:27:17,840
The next moon out - Europa - goes
round Jupiter precisely once
271
00:27:17,840 --> 00:27:19,840
for every two orbits of Io...
272
00:27:24,320 --> 00:27:27,000
..which means that every second
orbit,
273
00:27:27,000 --> 00:27:29,360
Io and Europa fall into
alignment.
274
00:27:31,520 --> 00:27:34,760
It's what's known as an orbital
resonance.
275
00:27:36,560 --> 00:27:38,880
That gives it a gravitational kick
276
00:27:38,880 --> 00:27:42,040
and that moves Io's orbit
into an ellipse.
277
00:27:42,040 --> 00:27:44,640
Now, that means that the
gravitational forces on Io
278
00:27:44,640 --> 00:27:47,840
are constantly shifting and
changing,
279
00:27:47,840 --> 00:27:50,840
and that stretches and squashes
the moon
280
00:27:50,840 --> 00:27:55,560
and heats it up - by friction.
Now, that is called tidal heating,
281
00:27:55,560 --> 00:27:58,920
and that is the origin of
Io's volcanoes.
282
00:28:11,280 --> 00:28:14,560
This process raises the temperature
in Io's interior,
283
00:28:14,560 --> 00:28:16,960
which would otherwise be
frozen solid,
284
00:28:16,960 --> 00:28:19,640
to more than
1,000 degrees Celsius...
285
00:28:22,920 --> 00:28:24,680
..creating its lava lakes...
286
00:28:28,120 --> 00:28:30,800
..and powering immense volcanic
plumes...
287
00:28:33,640 --> 00:28:37,440
..that rise up to 300km
from the moon's surface...
288
00:28:39,160 --> 00:28:40,800
..and out into space.
289
00:28:45,920 --> 00:28:49,840
Io provides the solar system
with a vivid reminder...
290
00:28:51,240 --> 00:28:53,200
..of the giant planet's power.
291
00:29:07,960 --> 00:29:10,840
Jupiter's intense gravitational
field...
292
00:29:13,000 --> 00:29:16,400
..is the source of Io's
volcanism today.
293
00:29:16,400 --> 00:29:19,360
But we don't feel that gravitational
pull here on Earth,
294
00:29:19,360 --> 00:29:21,840
because Jupiter is so far away,
295
00:29:21,840 --> 00:29:24,920
but four-and-a-half billion
years ago,
296
00:29:24,920 --> 00:29:29,120
Jupiter was migrating inwards
towards the inner solar system,
297
00:29:29,120 --> 00:29:32,880
approaching the region where
Mars and Earth were forming.
298
00:29:39,000 --> 00:29:43,160
After passing through what would
become the asteroid belt...
299
00:29:44,600 --> 00:29:46,880
..Jupiter entered the inner
solar system...
300
00:29:52,160 --> 00:29:55,680
..continuing its journey,
spiralling towards the sun.
301
00:30:03,800 --> 00:30:07,320
Back then, the area where Mars
and Earth orbit today
302
00:30:07,320 --> 00:30:10,400
was densely packed with
gas and rock.
303
00:30:18,560 --> 00:30:22,200
But as Jupiter approached,
it wrought havoc...
304
00:30:24,560 --> 00:30:28,040
..scattering the rocky material
in all directions...
305
00:30:30,640 --> 00:30:33,240
..some sent careering
into the sun...
306
00:30:42,080 --> 00:30:45,640
..others thrown out
into interstellar space.
307
00:30:53,040 --> 00:30:57,680
And it's this that may explain our
solar system's unusual structure.
308
00:31:00,720 --> 00:31:02,320
Here's the solar system today.
309
00:31:02,320 --> 00:31:07,000
{\an8}The sun, the four inner rocky
planets, the asteroids and Jupiter.
310
00:31:07,000 --> 00:31:10,560
{\an8}And what we think may have happened
is Jupiter made it inwards
311
00:31:10,560 --> 00:31:15,400
{\an8}through where the asteroids
are, as far in as the orbit of Mars.
312
00:31:15,400 --> 00:31:18,160
{\an8}And that would have cleaned out
quite a lot of the material
313
00:31:18,160 --> 00:31:22,640
{\an8}in the inner solar system, leaving
less for the formation of planets.
314
00:31:22,640 --> 00:31:26,560
And that's why we don't see
super-Earths in our solar system -
315
00:31:26,560 --> 00:31:28,600
those big, massive, rocky worlds
316
00:31:28,600 --> 00:31:32,480
that we see in orbit around so many
other stars.
317
00:31:32,480 --> 00:31:36,040
{\an8}This also might explain
why Mars is so small.
318
00:31:36,040 --> 00:31:39,760
{\an8}See, if Jupiter was orbiting
in the region that Mars was forming,
319
00:31:39,760 --> 00:31:42,480
{\an8}there would have been much less
material here.
320
00:31:42,480 --> 00:31:45,240
And that might explain why Mars
321
00:31:45,240 --> 00:31:48,880
is only a tenth of the mass
of Venus and Earth.
322
00:31:59,360 --> 00:32:01,640
Had Jupiter continued to move
inwards,
323
00:32:01,640 --> 00:32:04,640
it would have had a similar effect
on the Earth...
324
00:32:07,000 --> 00:32:10,440
..meaning the world we inhabit
might never have formed.
325
00:32:17,120 --> 00:32:21,720
But just as it looked as if Jupiter
would sweep everything away,
326
00:32:21,720 --> 00:32:25,200
something stopped the giant
planet in its tracks...
327
00:32:32,360 --> 00:32:36,520
..because in the shadows of the
outer solar system,
328
00:32:36,520 --> 00:32:38,480
another planet was forming.
329
00:32:43,160 --> 00:32:45,760
The solar system's second gas
giant...
330
00:32:47,520 --> 00:32:48,920
..Saturn.
331
00:33:01,360 --> 00:33:04,080
And its birth changed everything.
332
00:33:08,920 --> 00:33:12,280
When a planet forms in a disc
of material around a star,
333
00:33:12,280 --> 00:33:15,120
as Jupiter did in our solar system,
334
00:33:15,120 --> 00:33:19,400
it tends to clear out a gap
in the disc.
335
00:33:19,400 --> 00:33:22,680
Now, the material tends to fall
inwards towards the star.
336
00:33:22,680 --> 00:33:24,480
It's called the accretion
337
00:33:24,480 --> 00:33:27,200
and that drags the whole thing
inwards.
338
00:33:27,200 --> 00:33:29,920
And that's what happened to Jupiter.
339
00:33:29,920 --> 00:33:34,840
But, then, a less massive planet,
Saturn, formed further out.
340
00:33:34,840 --> 00:33:37,200
It cleared out its own disc
341
00:33:37,200 --> 00:33:40,680
and it too fell inwards
towards the sun,
342
00:33:40,680 --> 00:33:43,520
but more quickly than Jupiter.
343
00:33:43,520 --> 00:33:47,080
That meant that Saturn got
into a resonance with Jupiter.
344
00:33:47,080 --> 00:33:50,040
It went round once in orbit
around the sun
345
00:33:50,040 --> 00:33:52,280
for every two orbits of Jupiter,
346
00:33:52,280 --> 00:33:56,320
and that has the effect of cleaning
out the whole region
347
00:33:56,320 --> 00:33:58,360
between the two planets.
348
00:33:58,360 --> 00:34:00,040
And that has the effect,
349
00:34:00,040 --> 00:34:04,200
through a series of complicated
gravitational interactions,
350
00:34:04,200 --> 00:34:06,480
of slowing and stopping the in-fall
351
00:34:06,480 --> 00:34:11,120
and eventually causing the two
planets to move back out again.
352
00:34:11,120 --> 00:34:16,120
And that is what happened to Jupiter
and Saturn in our solar system.
353
00:34:24,240 --> 00:34:26,560
Saturn caused Jupiter to retreat...
354
00:34:27,680 --> 00:34:29,800
..leaving behind just enough
material
355
00:34:29,800 --> 00:34:32,280
from which the inner planets
could form.
356
00:34:35,760 --> 00:34:37,240
Mercury.
357
00:34:39,920 --> 00:34:41,200
Venus.
358
00:34:44,080 --> 00:34:45,440
Mars.
359
00:34:51,280 --> 00:34:53,520
And our home...
360
00:34:53,520 --> 00:34:54,960
..the Earth.
361
00:35:01,320 --> 00:35:05,040
By preventing the formation of much
larger super-Earths,
362
00:35:05,040 --> 00:35:08,000
Jupiter allowed our planet to grow.
363
00:35:22,640 --> 00:35:27,640
And even as Jupiter's reign of
terror was drawing to a close,
364
00:35:27,640 --> 00:35:31,560
it provided one last parting
gift to our world.
365
00:35:45,920 --> 00:35:49,440
The young Earth formed in an arid
region of the inner solar system.
366
00:35:49,440 --> 00:35:52,840
There was very little water
that close to the sun,
367
00:35:52,840 --> 00:35:56,560
but as the Earth was forming,
Jupiter was already tacking back
368
00:35:56,560 --> 00:35:58,960
outwards again into the
outer solar system,
369
00:35:58,960 --> 00:36:03,000
through the region that we now call
the asteroid belt,
370
00:36:03,000 --> 00:36:07,720
a region populated by many icy,
water-rich comets and asteroids.
371
00:36:07,720 --> 00:36:10,440
And they were scattered back
inwards again,
372
00:36:10,440 --> 00:36:13,640
bringing water back into the
inner solar system.
373
00:36:13,640 --> 00:36:15,840
So, I think it is quite a wonderful
thought,
374
00:36:15,840 --> 00:36:21,200
that Earth is a water world today
because of the motion inwards
375
00:36:21,200 --> 00:36:24,760
and then back outwards again
of the massive planet Jupiter.
376
00:36:31,000 --> 00:36:36,720
This idea does seem quite
contrived, almost fantastical,
377
00:36:36,720 --> 00:36:39,840
but the more we learn about
the formation of solar systems,
378
00:36:39,840 --> 00:36:43,600
and the more we try to model
a system like ours,
379
00:36:43,600 --> 00:36:47,440
with four terrestrial, water-rich
planets close to the star
380
00:36:47,440 --> 00:36:50,240
and then the gas giants further out,
381
00:36:50,240 --> 00:36:54,720
the more we learn that perhaps all
these things had to happen,
382
00:36:54,720 --> 00:36:59,120
these unlikely movements and
interactions between the planets,
383
00:36:59,120 --> 00:37:05,320
in order to produce a system like
ours and a planet like ours.
384
00:37:05,320 --> 00:37:09,440
So, places like this may
be extremely rare.
385
00:37:24,640 --> 00:37:28,040
Today, Jupiter has settled
into a regular orbit
386
00:37:28,040 --> 00:37:31,360
back beyond the far edge
of the asteroid belt...
387
00:37:34,280 --> 00:37:38,360
..its days of marauding through
the solar system at an end.
388
00:38:21,600 --> 00:38:24,280
Jupiter has been established
in a stable orbit
389
00:38:24,280 --> 00:38:26,400
for almost four billion years.
390
00:38:26,400 --> 00:38:29,840
If I was to sit here on Earth
3.8 billion years ago
391
00:38:29,840 --> 00:38:32,640
when life began and look
up into the night sky,
392
00:38:32,640 --> 00:38:36,280
I would have seen it shining
there as a point of light
393
00:38:36,280 --> 00:38:40,400
the same as it looks today,
distant and seemingly detached.
394
00:38:40,400 --> 00:38:44,400
And it's remained that way for the
vast expanse of time it's taken
395
00:38:44,400 --> 00:38:46,680
for evolution by natural selection
396
00:38:46,680 --> 00:38:52,120
to transform those first populations
of organisms into all this,
397
00:38:52,120 --> 00:38:55,680
to transform the Earth into an
oasis of life
398
00:38:55,680 --> 00:38:57,800
in the desert of the solar system.
399
00:39:08,240 --> 00:39:12,520
But Jupiter's influence over the
Earth remains to this day...
400
00:39:16,840 --> 00:39:20,720
..and that's because, despite its
great distance from us...
401
00:39:22,080 --> 00:39:25,760
..it retains a vice-like grip
over the asteroid belt.
402
00:39:40,720 --> 00:39:42,760
It's easy, I think quite natural,
403
00:39:42,760 --> 00:39:45,280
to think of the asteroid belt
as a single structure.
404
00:39:45,280 --> 00:39:47,840
A sort of ring of rock surrounding
the sun.
405
00:39:47,840 --> 00:39:50,560
But that's not
what it's like at all.
406
00:39:50,560 --> 00:39:54,520
In reality, each one of those
millions and millions of pieces
407
00:39:54,520 --> 00:39:58,600
of rock is following its own
individual orbits.
408
00:39:58,600 --> 00:40:01,000
And this remarkable animation
409
00:40:01,000 --> 00:40:04,680
is made up of ten years
of astronomical observations.
410
00:40:04,680 --> 00:40:08,760
And every point you see
on this animation...
411
00:40:08,760 --> 00:40:12,320
..is a single asteroid,
apart from all the planets.
412
00:40:12,320 --> 00:40:16,560
And so you see Earth and Mars
and Venus whizzing around the sun.
413
00:40:16,560 --> 00:40:19,960
But the interesting one
is Jupiter...
414
00:40:19,960 --> 00:40:23,080
..orbiting just outside the
asteroid belt.
415
00:40:24,280 --> 00:40:27,400
What you can see is that the
asteroid belt
416
00:40:27,400 --> 00:40:29,400
dances to Jupiter's tune.
417
00:40:29,400 --> 00:40:32,520
It's the conductor of the asteroid
belt, if you like.
418
00:40:32,520 --> 00:40:36,760
There are complex patterns
here, but there's also structure.
419
00:40:38,720 --> 00:40:42,320
And the reason for that is
the delicate interplay
420
00:40:42,320 --> 00:40:44,600
between the gravitational pull
of the sun
421
00:40:44,600 --> 00:40:47,560
and the gravitational force from
Jupiter.
422
00:40:49,440 --> 00:40:50,760
Now, what can happen is that,
423
00:40:50,760 --> 00:40:53,560
perhaps because of an interaction
between two asteroids,
424
00:40:53,560 --> 00:40:55,720
perhaps they collide with
each other,
425
00:40:55,720 --> 00:40:59,360
or perhaps on their orbit
they line-up perfectly with Jupiter
426
00:40:59,360 --> 00:41:01,560
and get an extra gravitational kick,
427
00:41:01,560 --> 00:41:04,440
those asteroids can be disturbed
from this structure
428
00:41:04,440 --> 00:41:07,400
and be sent
inwards to the inner solar system.
429
00:41:07,400 --> 00:41:12,560
And by that mechanism, Jupiter
has a profound influence
430
00:41:12,560 --> 00:41:14,960
on the planets closer to the sun.
431
00:41:24,960 --> 00:41:27,760
Around 100 million years ago,
432
00:41:27,760 --> 00:41:32,160
an asteroid 10km across was ejected
from the asteroid belt.
433
00:41:36,640 --> 00:41:39,680
Dislodged by Jupiter's gravity,
434
00:41:39,680 --> 00:41:43,160
it was set on a collision
course with the Earth.
435
00:42:02,440 --> 00:42:06,080
When it struck, it generated
a fireball so hot,
436
00:42:06,080 --> 00:42:11,280
anything within a 1,000km
radius would have died instantly.
437
00:42:20,000 --> 00:42:23,680
The impact threw 300 billion
tonnes of sulphur
438
00:42:23,680 --> 00:42:25,000
into the atmosphere.
439
00:42:34,080 --> 00:42:37,400
And during the nuclear winter
that followed,
440
00:42:37,400 --> 00:42:42,440
75% of all species were wiped
from the face of the Earth.
441
00:42:50,280 --> 00:42:52,320
In one fell swoop,
442
00:42:52,320 --> 00:42:55,840
Jupiter changed the course
of our planet's history.
443
00:43:08,240 --> 00:43:10,760
There are a few places
on Earth today
444
00:43:10,760 --> 00:43:13,760
where you can catch a glimpse
of lost worlds,
445
00:43:13,760 --> 00:43:17,400
you can see Earth as it was millions
of years in the past
446
00:43:17,400 --> 00:43:21,200
and perhaps glimpse the Earth as it
might have been.
447
00:43:21,200 --> 00:43:22,760
And this is one of them.
448
00:43:22,760 --> 00:43:25,080
Today, this is the Colorado Plain,
449
00:43:25,080 --> 00:43:26,760
over a kilometre in altitude,
450
00:43:26,760 --> 00:43:29,480
south of Denver,
close to the Rocky Mountains,
451
00:43:29,480 --> 00:43:34,080
but 200 million years ago
this was at sea level.
452
00:43:34,080 --> 00:43:38,680
It was an ancient lake and the
ghosts of those lost worlds,
453
00:43:38,680 --> 00:43:41,280
the imprints of the past, can be
seen over there,
454
00:43:41,280 --> 00:43:45,520
because there are literally
thousands of dinosaur footprints.
455
00:44:11,480 --> 00:44:14,320
And here they are,
the dinosaur footprints.
456
00:44:14,320 --> 00:44:17,440
I find this absolutely remarkable.
457
00:44:17,440 --> 00:44:20,640
This is the footprint
of a sauropod dinosaur.
458
00:44:20,640 --> 00:44:24,120
That's one of the big ones. The big
herbivores with the long necks.
459
00:44:24,120 --> 00:44:26,520
This animal would have weighed
about 30 tonnes.
460
00:44:26,520 --> 00:44:30,600
It was tall enough to peer
over a two-storey house.
461
00:44:30,600 --> 00:44:34,360
What happened here is, probably
a herd of them, a group of them
462
00:44:34,360 --> 00:44:37,960
came lumbering across this lake bed
and then,
463
00:44:37,960 --> 00:44:41,160
perhaps that same afternoon,
the predators came,
464
00:44:41,160 --> 00:44:43,640
maybe following the herd.
465
00:44:43,640 --> 00:44:45,840
And that's these footprints here.
466
00:44:45,840 --> 00:44:48,640
The allosaurus', these three-toed
footprints.
467
00:44:48,640 --> 00:44:51,960
Much smaller animal, maybe
about twice the height of me,
468
00:44:51,960 --> 00:44:55,200
about two tonnes,
very nimble and agile.
469
00:44:55,200 --> 00:44:59,960
And so you see a whole story
played out here, frozen in time.
470
00:45:14,120 --> 00:45:17,320
Today, just their traces remain...
471
00:45:22,760 --> 00:45:24,800
..but were it not for Jupiter...
472
00:45:26,240 --> 00:45:27,880
..they might still be here.
473
00:45:45,640 --> 00:45:47,600
There are so many chance events,
474
00:45:47,600 --> 00:45:50,080
not only throughout the history
of Earth,
475
00:45:50,080 --> 00:45:53,000
but also spanning the entire history
of the universe
476
00:45:53,000 --> 00:45:57,480
for 13.8 billion years, without
which we wouldn't exist.
477
00:45:57,480 --> 00:45:59,880
There's an unbroken chain of life
stretching back
478
00:45:59,880 --> 00:46:01,800
four billion years here on this
planet.
479
00:46:01,800 --> 00:46:04,880
You interrupt or interject
at any point
480
00:46:04,880 --> 00:46:07,640
and life on Earth is different.
481
00:46:07,640 --> 00:46:11,680
But having said that, there are
major events that affected life.
482
00:46:11,680 --> 00:46:15,120
And one of them is the asteroid
that wipes out the dinosaurs.
483
00:46:15,120 --> 00:46:18,280
And, in that sense, it is certainly
true to say
484
00:46:18,280 --> 00:46:21,240
that without Jupiter, we
wouldn't be here.
485
00:46:38,240 --> 00:46:41,040
The godfather of the planets
paved the way for us
486
00:46:41,040 --> 00:46:42,720
to inherit the Earth.
487
00:46:48,520 --> 00:46:50,480
And although it occasionally
flings rocks
488
00:46:50,480 --> 00:46:52,360
from the asteroid belt our way...
489
00:46:53,520 --> 00:46:55,960
..it also protects us...
490
00:47:02,400 --> 00:47:04,720
..because for objects heading
towards the Earth
491
00:47:04,720 --> 00:47:07,920
from the far reaches of the solar
system,
492
00:47:07,920 --> 00:47:11,480
Jupiter's gravitational
field acts as a shield.
493
00:47:16,920 --> 00:47:20,160
Around a century ago, a lump
of rock and ice
494
00:47:20,160 --> 00:47:25,480
4km across and weighing
17 billion tonnes...
495
00:47:27,080 --> 00:47:30,240
..was hurtling towards the inner
solar system...
496
00:47:34,720 --> 00:47:37,800
..until Jupiter intervened.
497
00:47:40,600 --> 00:47:45,680
Five, four, three, two, one...
498
00:47:45,680 --> 00:47:47,760
We have ignition and lift off of
Atlantis
499
00:47:47,760 --> 00:47:51,000
and the Galileo Spacecraft
bound for Jupiter.
500
00:47:52,280 --> 00:47:56,600
70 years later, we witnessed
just how effective a shield
501
00:47:56,600 --> 00:47:58,240
Jupiter can be.
502
00:48:07,160 --> 00:48:09,720
Onboard the space shuttle
Atlantis...
503
00:48:11,040 --> 00:48:12,520
..the Galileo orbiter.
504
00:48:22,360 --> 00:48:24,760
Three years after Galileo launched,
505
00:48:24,760 --> 00:48:29,720
comet Shoemaker-Levy-9 had been
captured by Jupiter's gravity.
506
00:48:38,760 --> 00:48:41,640
Locked in the giant planet's
embrace...
507
00:48:43,520 --> 00:48:46,680
..tidal forces now began to
tear it apart.
508
00:48:54,040 --> 00:48:56,000
Its journey cut short...
509
00:48:57,080 --> 00:48:59,600
..the comet now faced annihilation.
510
00:49:11,120 --> 00:49:13,760
After crossing the inner
solar system,
511
00:49:13,760 --> 00:49:16,720
Galileo passed through the
asteroid belt...
512
00:49:20,120 --> 00:49:22,520
..approaching the spots from where
it would witness
513
00:49:22,520 --> 00:49:24,400
the comet's final moments.
514
00:49:35,200 --> 00:49:40,240
On July 16th, Galileo saw the first
fragments of the comet
515
00:49:40,240 --> 00:49:43,000
{\an8}enter Jupiter's southern hemisphere.
516
00:49:55,120 --> 00:49:57,560
Pieces of comet Shoemaker-Levy-9
517
00:49:57,560 --> 00:50:00,760
struck Jupiter over the course of
six days.
518
00:50:04,760 --> 00:50:08,520
It was the first time a comet strike
had ever been witnessed.
519
00:50:29,640 --> 00:50:32,800
The most destructive impact released
energy
520
00:50:32,800 --> 00:50:36,040
equivalent to six million megatons
of TNT...
521
00:50:37,800 --> 00:50:43,160
..leaving behind a giant dark
cloud 12,000km across.
522
00:50:52,560 --> 00:50:57,320
By capturing objects
and incinerating them on impact...
523
00:50:57,320 --> 00:51:01,400
..Jupiter sweeps up bodies
from the outer solar system...
524
00:51:01,400 --> 00:51:04,320
..that might otherwise collide
with Earth.
525
00:51:17,200 --> 00:51:19,080
Jupiter,
526
00:51:19,080 --> 00:51:22,280
the oldest and largest of
the planets,
527
00:51:22,280 --> 00:51:24,960
is the godfather of our
solar system.
528
00:51:28,640 --> 00:51:29,680
In youth...
529
00:51:30,720 --> 00:51:32,400
..it went on the rampage.
530
00:51:40,960 --> 00:51:43,920
For some young planets,
it spelt disaster.
531
00:51:49,320 --> 00:51:52,040
But for others,
like our own world,
532
00:51:52,040 --> 00:51:54,560
it cleared the way for their
formation.
533
00:52:03,200 --> 00:52:06,040
And in adulthood, it created
the conditions
534
00:52:06,040 --> 00:52:07,760
that allowed us to rise.
535
00:52:12,600 --> 00:52:15,800
So we owe Jupiter a great debt.
536
00:52:17,560 --> 00:52:20,760
But, as the dinosaurs found
to their cost,
537
00:52:20,760 --> 00:52:24,360
it's a debt that could be recalled
at any time.
538
00:52:29,240 --> 00:52:30,480
To the naked eye,
539
00:52:30,480 --> 00:52:33,800
Jupiter is one of the brightest
points of light in the night sky,
540
00:52:33,800 --> 00:52:37,920
and through a small telescope, it is
a beautiful banded world.
541
00:52:37,920 --> 00:52:41,160
But it feels distant, eternal,
542
00:52:41,160 --> 00:52:44,200
disconnected from events
here on Earth.
543
00:52:44,200 --> 00:52:48,080
But the more we've understood about
the history of the solar system,
544
00:52:48,080 --> 00:52:51,240
the more we've come to understand
that that is not the case.
545
00:52:51,240 --> 00:52:55,640
Jupiter has played an important
and perhaps decisive role
546
00:52:55,640 --> 00:52:59,000
in the stories of all the planets,
including Earth.
547
00:52:59,000 --> 00:53:02,560
So the solar system is just that -
it's a system,
548
00:53:02,560 --> 00:53:06,680
complex, interconnected and
interdependent.
549
00:53:06,680 --> 00:53:10,760
So next time you see Jupiter,
just hold your gaze,
550
00:53:10,760 --> 00:53:15,960
maybe think for a minute, because it
is so much more than just a point
551
00:53:15,960 --> 00:53:18,040
of light, or a planet, even.
552
00:53:18,040 --> 00:53:21,440
It is the great sculptor
of the solar system,
553
00:53:21,440 --> 00:53:24,360
the destroyer and creator of worlds.
554
00:54:05,840 --> 00:54:07,920
I think people are drawn
in by Jupiter
555
00:54:07,920 --> 00:54:10,800
because it's very mysterious.
556
00:54:10,800 --> 00:54:14,280
It's covered by clouds that hide
what's underneath.
557
00:54:14,280 --> 00:54:15,600
It's very violent.
558
00:54:17,240 --> 00:54:19,360
And it's very intimidating.
559
00:54:21,480 --> 00:54:23,280
It's also very beautiful.
560
00:54:24,280 --> 00:54:26,520
It has all these things going on
561
00:54:26,520 --> 00:54:29,400
and it's hard not to be taken in.
562
00:54:29,400 --> 00:54:34,760
T-minus ten, nine, eight,
seven, six...
563
00:54:34,760 --> 00:54:37,120
Such is Jupiter's mystique,
564
00:54:37,120 --> 00:54:40,960
it's been a recurring
target for space exploration.
565
00:54:40,960 --> 00:54:47,000
And lift off of the Atlas V with
Juno on a trek to Jupiter.
566
00:54:47,000 --> 00:54:51,640
In 2011, Nasa launched its latest
mission - Juno.
567
00:55:00,840 --> 00:55:03,080
When we launched the Juno spacecraft
568
00:55:03,080 --> 00:55:06,040
away from the Earth out towards
Jupiter,
569
00:55:06,040 --> 00:55:11,200
we didn't have enough speed to get
away out of the gravity of the sun,
570
00:55:11,200 --> 00:55:14,160
so we actually had to come back
to Earth,
571
00:55:14,160 --> 00:55:16,560
get a gravity assist from Earth,
572
00:55:16,560 --> 00:55:18,480
and then go out to Jupiter.
573
00:55:22,840 --> 00:55:26,680
After travelling for five
years, Juno finally arrived.
574
00:55:31,160 --> 00:55:35,200
This is a mission that goes closer
to the planet in its orbit
575
00:55:35,200 --> 00:55:37,160
than any other mission ever has.
576
00:55:37,160 --> 00:55:41,800
Only a few thousand kilometres from
the cloud tops and very, very fast.
577
00:55:41,800 --> 00:55:44,120
We go from pole to pole in
two hours,
578
00:55:44,120 --> 00:55:47,720
slipping between the radiation belts
in the cloud tops,
579
00:55:47,720 --> 00:55:50,560
getting the data as fast as we can
and getting out.
580
00:55:52,680 --> 00:55:55,320
So, in every way, Juno is
breaking new ground
581
00:55:55,320 --> 00:55:59,720
and that's allowed us to see things
that we couldn't have ever imagined.
582
00:56:04,480 --> 00:56:08,520
Juno's mission is to explore
the planets inside and out.
583
00:56:10,920 --> 00:56:14,240
And amongst the many scientific
instruments it has on board
584
00:56:14,240 --> 00:56:17,160
is its camera, JunoCam.
585
00:56:19,280 --> 00:56:24,080
You see all these swirls, you see
all sorts of spots coming up.
586
00:56:24,080 --> 00:56:29,880
You see all these vortices, you see
dramatic storm systems interacting.
587
00:56:35,440 --> 00:56:38,360
It's mind-blowingly beautiful
pictures
588
00:56:38,360 --> 00:56:41,280
that this little camera
has been taking.
589
00:56:43,960 --> 00:56:47,440
JunoCam was able to see
the Great Red Spot from up close.
590
00:56:49,120 --> 00:56:51,400
We can see height to the clouds.
591
00:56:51,400 --> 00:56:54,080
We can see features that look
like storms.
592
00:56:54,080 --> 00:56:58,400
Maybe it's hailing or snowing
ammonia on Jupiter.
593
00:57:01,800 --> 00:57:07,160
And the most startling thing that we
saw from JunoCam's imagery
594
00:57:07,160 --> 00:57:10,200
was that the poles of Jupiter
are actually blue.
595
00:57:14,040 --> 00:57:16,520
They are nothing like the orange
and white planet
596
00:57:16,520 --> 00:57:19,360
that we grew up thinking about
as children.
597
00:57:24,520 --> 00:57:28,400
Juno has just begun to unlock
Jupiter's secrets.
598
00:57:31,240 --> 00:57:33,120
And so, at last,
599
00:57:33,120 --> 00:57:36,760
the godfather of the planets
has begun to talk.
600
00:57:51,960 --> 00:57:56,000
A planet that began life
as an unremarkable rocky world...
601
00:57:57,600 --> 00:58:01,840
..but transformed into one
of the jewels of the solar system...
602
00:58:03,360 --> 00:58:08,440
..where shimmering rings of ice
harbour a potential home for life.
603
00:58:11,120 --> 00:58:12,320
Saturn.
604
00:58:16,440 --> 00:58:19,720
Journey through our solar system
with the Open University
605
00:58:19,720 --> 00:58:23,520
and discover more about its
planets and moons.
606
00:58:25,160 --> 00:58:28,160
Explore this and more with our
academic experts.
607
00:58:30,920 --> 00:58:34,480
Go to...
608
00:58:35,760 --> 00:58:38,840
..and follow the links
to the Open University.
51395
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