Space's Deepest Secrets (2016–…): Season 8, Episode 5 - The Giant Ice Planets - full transcript
Astronomers finally unlock the mysteries of Uranus and Neptune.
Uranus and Neptune.
Two of the largest,
farthest
and strangest planets
in our solar system.
Of all the big planets,
Uranus and Neptune
remain the biggest enigmas.
Today, astronomers
are finally unlocking
why these supersized snowballs
are so weird.
In Uranus
and Neptune, we have two planets
that just don't like
playing by the rules.
Can an ancient mega-collision
reveal what knocked
Uranus onto its side?
Can a missing twin world
unlock why one of Neptune's
moons orbits the wrong way?
This is a large moon
but yet it's orbiting
the planet backwards.
That's a mystery that
needs explaining.
And what is the
energy that drives the fastest winds
in the solar system?
It's a rare planet that has winds
faster than the speed of sound.
To find out, we
venture to these frozen planets
explore their alien underworlds
to reveal what makes
these ice giants
the weirdest worlds
in the solar system.
At the limits of our
solar system lie two huge planets.
Uranus
and Neptune.
Both are over 14 times
the mass of Earth.
They orbit more than 2.8
billion miles away from the Sun.
This makes them the farthest out,
confirmed planets in the solar system.
And the most mysterious.
We have sent orbiters
to every major planet
in the solar system
except Uranus and Neptune.
Uranus and Neptune
are really far away
and sending a space probe
out there is pretty hard.
Only one NASA mission
has ventured out
for a closer look.
Voyager 2 flies past Uranus
in 1986
and Neptune in 1989.
The spacecraft reveals
that these planets,
sculpted from frozen water,
methane and ammonium,
are far from dead.
The thing that's
so poignant about the ice giant worlds,
is that we've only visited them
for a couple of days.
The Voyager spacecraft
just flew on by.
And yet,
in that brief encounter,
we saw things we never expected.
Instead of cold, boring worlds
like we maybe
thought they would be,
they were exciting.
They had weather.
They turned out to be much more
dynamic than we ever imagined.
As Voyager 2 flies by,
it captures
detailed photographs,
of the strange moons
that orbit the ice giants.
Uranus has 27 moons.
Neptune has 14.
The ice giants have
some of the most fascinating
moons in the solar system.
You have Naiad and Thalassa,
two moons of Neptune
that are locked
in this gravitational dance
with one another.
And they zig-zag up and down
unlike any other moons
in the solar system.
Uranus has Miranda,
this moon that seems to have
been cracked apart and reassembled,
with vast craters and
giant cliffs and fields of ice.
The weirdest moon
of all is Triton.
Triton is around half the size
of Earth's moon.
But it is 400 times more massive than
Neptune's next largest moon, Proteus.
Two-thirds
of Triton is rock and metal.
The rest is a crust of water
and nitrogen ice,
frozen to a temperature of
minus 390 degrees Fahrenheit.
This ice world is unlike any other
large moon in the solar system.
Triton is really unique
in that it's the only large
moon in the solar system
with a retrograde orbit.
That's an orbit that is opposite to
the direction of the planet's spin.
Scientists think that
most planets and their moons
form from the same
spinning cloud of gas and dust.
The center of the spinning cloud
collapses to form
a rotating planet
while the outer edge condenses
into the planet's moons.
Everything turns
in the same direction
as the original cloud.
So, how does Triton end up
orbiting Neptune in reverse?
Today, new technologies
and discoveries
make it possible
to finally unlock
the mysteries of the ice giants.
A clue about Triton's
strange orbit
lies in the data collected by one
of NASA's most ambitious missions
to the outer solar system.
In 2015,
NASA's New Horizons probe
flies past Pluto.
Pluto is a dwarf planet.
It is the largest object
in the Kuiper belt,
a massive ring
of billions of space rocks
that lies beyond
the orbit of Neptune,
on the fringes
of the solar system.
New Horizons beams back to Earth
breathtaking images
of this frozen world.
Pluto just blew me away.
We saw glaciers
made of nitrogen ice.
And one of my favorite images
from the past decade
is sunlight glinting off of
mountains of pure water ice.
The scientific
instruments on board the probe
analyzed Pluto's
vital statistics
to unlock what the
dwarf planet is made from.
The instruments revealed
that Pluto and Triton
are almost exactly the same.
The bodies are roughly
the same size.
Both Pluto and Triton have
cores made from rock and metal.
And their crusts consist of layers of
frozen nitrogen, water and methane.
This evidence points to
an incredible possibility.
One that could solve the mystery
of why Triton
orbits Neptune backwards.
Triton and Pluto
are in many ways
geological twins.
One of the simplest explanations
that could account for that
is that they originated
from the same place.
That place is the Kuiper Belt.
Why did Triton break out
from this ring of rocks?
Astronomers think that
Neptune's size
could reveal the answer.
Neptune is 17 times
more massive than Earth.
This mass gives the planet
a super-strong
gravitational influence.
It is possible that over time
Neptune's huge gravity
gradually pulls Triton away
from this ring of rocks
to eventually capture it
as its moon.
But there is one problem
with this theory:
the speed of the objects
inside the Kuiper Belt.
If you do the
calculations what you will find is,
by the time a solitary Triton
passes by Neptune,
it's moving too fast
to be captured.
Neptune's gravity would
have deflected it,
but it would have
just kept on going.
In order for Triton to end up
in orbit around Neptune,
something would have had to
hit the brakes and slowed it down.
What slowed down Triton enough
for Neptune to capture it?
And how did this dwarf planet
end up orbiting
Neptune backwards?
The giant ice planet, Neptune,
has a weird moon.
Triton orbits
in the opposite direction
to Neptune's rotation.
One explanation is that
the planet pulled Triton
from the Kuiper Belt.
But what slowed down
Triton enough
to allow Neptune to capture it
travelling the wrong way?
Astronomers believe
that one of Pluto's moons
offers a clue.
Charon is half
the size of Pluto.
This closeness in size
makes the pair
dance around each other
as they orbit the sun.
Pluto is not much bigger
like all the other
planets and moons.
So instead of being like,
a single large body
with a smaller one orbiting it,
it's more like a dumbbell,
and this dumbbell
orbits as one thing.
Astronomers call two
orbiting bodies of a similar size
a binary system.
The strange orbit of binaries
could unlock how Triton
slows down enough
for Neptune to capture it
travelling the wrong way.
When objects in the
Kuiper Belt pick up a partner,
they completely change
the way they move
through the cosmos.
Once they've caught each other,
they start revolving around
their common center of gravity.
This disrupts their trajectory,
as on every turn,
one partner must move backwards
against their orbit.
Once every pirouette,
they can slow down so much
that they become vulnerable
to capture.
Some astronomers believe that
Triton once had
its own binary partner,
just like Pluto
has Charon today.
They think that
this missing binary
is the key that unlocks
how Neptune captures Triton.
The discovery that
ten to fifteen percent of
Kuiper Belt objects are binary
may solve the Triton problem.
If Triton itself was a binary,
it had a large companion
when it passed by Neptune.
That could have put
the brakes on it
and allowed it to orbit Neptune.
Triton and its companion
orbit each other
inside the Kuiper Belt.
Over time,
Neptune's gravity
gradually pulls
the pair away from the Belt.
They fall towards
the giant planet
and slingshot around it.
Thanks to their binary dance,
there is a point when
Triton moves slowly enough
for Neptune to capture it.
This breaks the
gravitational bond
between Triton and its partner
and hurls its companion
across the solar system.
Triton is left alone
orbiting Neptune the wrong way.
This companion was kind of
a sacrificial lamb
that got kicked out
into the depths of space
in order for Triton itself to be
captured into Neptune's orbit.
Triton's strange orbit
is just one of this
weird moon's mysteries.
Voyager 2
photographs Triton up-close
in 1989.
The camera on board
captures something weird
on the surface
of this strange world.
Hidden in this grainy photograph
is a mysterious plume
that rises from
the surface of Triton.
The plume is a geyser
of frozen nitrogen
five miles high.
Winds in the moon's
thin upper atmosphere
blow the vapor into trails
that are hundreds of miles long.
When Voyager flew past Triton,
it saw the unexpected.
There were jets of gas shooting
out from the moon's surface.
No one expected that.
It's out at the far reaches
of the solar system.
We expected to find
a cold, dead moon.
What the heck is going on?
Why do geysers
blast from the surface of Triton?
And what is the power source
that drives them?
In 2019,
investigators used the
Gemini South telescope in Chile
to study Triton's icy crust.
Researchers discovered that
the ice on the surface of Triton
is a special cocktail
of carbon monoxide
and frozen nitrogen.
In some ways
you can think of Triton
as having a frozen atmosphere.
Our atmosphere on Earth
is mostly nitrogen
and that's true on Triton too.
But the nitrogen's frozen
into a layer of ice.
That ice is actually
transparent to light.
So, sunlight can get through
that transparent ice
and heat up
little pockets in it.
Some types of ice
transform directly
from a solid into gas,
when they heat up
inside an atmosphere
that is super thin.
Astronomers believe that
this volatility of Triton's ice
unlocks they mystery
of its mega geysers.
At a point in Neptune's year,
Triton's north pole
leans towards the Sun.
This gives one hemisphere
of the moon
a summer that lasts
41 Earth years.
The rays from the Sun are weak
but they can pass through
Triton's nitrogen ice.
Here, they hit
a dark layer of dust
which heats up
by just a few degrees.
Enough to turn the ice above
into gas.
The pressure rises
as the gas builds up,
until it erupts as
powerful geysers of nitrogen.
Voyager 2 shows that ice
giants contain many secrets.
The data it beams back to Earth
reveals another mystery
for astronomers to solve.
The magnetometer
on board the probe
detects that
the magnetic field of Uranus
is super strange.
The field lines
continually twist and shift.
The magnetic poles are offset
from the planet's
axis of rotation
by a massive 60 degrees.
Voyager 2 discovers later
that the magnetic field
of Neptune
is also irregular
and misaligned.
When you think about
the magnetic of a planet,
sometimes you get something
very simple, like the Earth.
It's almost as if
there's a giant bar magnet
going right through
the core of our planet
with a very clear
north pole and south pole.
With the ice giant,
something altogether different
is going on.
The magnetic fields are chaotic.
The magnetic field lines
twist and turn
like a bag of writing snakes.
And the south pole of the planet
is actually along the equator.
Why are the magnetic
fields of the ice giants twisted?
Can a strange material
deep inside Uranus
unlock the mystery?
Uranus and Neptune
lie at the farthest reaches
of our solar system.
Voyager 2 remains
the only mission
to visit these
ice giant planets.
The spacecraft discovers
that they have strange moons
and bizarre,
twisted magnetic fields.
Why are the magnetic fields of
Uranus and Neptune so chaotic?
Scientists believe
the answer lies
in discovering what
inside the ice giants
generates their magnetic fields?
A mass of molten iron and nickel
sits at the center
of a rocky planet like Earth.
This super dense liquid metal
forms a thick and compact shell
wrapped around
the planet's core.
Heat drives powerful currents
inside this concentration
of molten material.
These deep currents
generate a magnetic field.
The rotation of Earth
twists the currents
into orderly streams that
move in the same direction
as Earth turns.
The result is that the axis
of Earth's magnetic field
almost matches the axis
of the planet's rotation.
Well, the magnetic field
is generated
by rotating liquids
inside the planet
and those liquids
are going to rotate
along with the planet itself.
So, it makes sense that
the planet's geographic
north and south pole
align with the magnetic
north and south pole.
However, with Uranus,
we don't see that.
An ice giant
contains no moving metal
at its core.
Scientists believe
the cores of these planets
are made from a mixture of
rock, water,
methane and ammonia.
So, what happens at
the center of ice giants?
Scientists at the University
of Rochester in New York
believe that the huge pressure
at the core of ice giants
helps unlock the mystery.
In 2018,
they test how this pressure
transforms water
into weird states of matter
with strange properties.
They use an anvil
made of diamonds
to compress a sample of water
to a pressure similar to that
at the core of an ice giant.
The crust water transforms
at the molecular level
and turns into a super-hot
jet black material
called superionic ice.
Its oxygen atoms
form a rigid lattice
that hydrogen atoms
can float through,
meaning that it can become
electrically charged.
But this weird ice is rigid.
So if it is at the core
of the ice giants
it creates
a fundamental problem.
Only moving material
inside a planet
can act like a dynamo
and generate a magnetic field.
The Rochester experiment
shows that an ice giant's core
could be static.
This means that
the planet's magnetic field
can't come from there.
Water ice
under the right conditions
very compressed
to the core of a planet
is actually stopping
the magnetic field
going through the very center
of the planet.
So there's gonna be
no magnetic field
based in the core of Uranus.
If the super pressurized
ice core of an ice giant
doesn't generate
the planet's magnetic field,
then what does?
One theory is that a liquid
ocean of compressed water
exists in a thin shell
around the solid core
of an ice giant.
Farther up from the core,
there's this sort of
a Goldilocks Zone.
Not too compressed,
the water can flow around
yet still be
electrically charged,
and there's your magnetic field.
How this layer
of pressurized liquid
moves around this solid
superionic ice core,
could unlock why
the magnetic fields
of ice giants are chaotic.
Deep inside Uranus...
...lies a compressed
superionic ice core
that is a scorching
9,000 degrees Fahrenheit.
Somewhere in between
this rigid ball
and the surface of the planet
is a shell of highly
pressurized water that can flow.
But the disconnected currents
inside this layer
do not generate
a magnetic field that matches
the direction
of the planet's rotation.
So that's how the magnetic
fields of the ice giants
can slip and become misaligned.
Weird water unlocks
why the ice giants
have super strange
magnetic fields.
But these mega planets
contain more mysteries
for astronomers to solve.
Voyager 2 sees up close, arguably,
the single strangest characteristic
of either of these
distant planets.
There's a lot of
weird stuff about Uranus
but maybe the weirdest is
that it orbits the Sun on its side.
Uranus leans over
98 degrees from the vertical.
It is the only planet
in the solar system
that is orientated this way.
Why does this ice giant
roll around the Sun
like a huge beach ball?
Astronomers think
that planets form
from a disc of gas and dust...
orbiting a young star.
These young worlds inherit both
their direction and axes of spin
from the angle of the disc.
This means that
all of the planets
should be born with a spin axis
that is roughly
90 degrees to the disc.
This model predicts that
Uranus starts life upright,
just like all the other
planets in the solar system.
So what tips Uranus
onto its side after it forms?
Scientists believe that a clue lies
in our solar system's violent past.
The early days
of the solar system
were a chaotic maelstrom
of smash-and-grabs.
We see evidence of this, of
course, in the form of craters
on many bodies
in the solar system.
Does an ancient
mega-collision knock Uranus onto its side?
And what are the mysterious
spots in the atmosphere of Neptune?
Uranus leans over so
much that it orbits the Sun on its side.
One explanation is that
Uranus is involved
in a mega-collision
billions of years ago.
But what kind of cosmic crash
can knock over an entire planet?
Researchers at the University
of Durham in the United Kingdom
simulate impacts between
Uranus and large protoplanets.
They build a virtual Uranus
and fire space objects at it
from different angles.
These simulations show
that a head-on collision
blows apart the virtual Uranus.
But a sideswipe generates
just the right amount of force
to leave Uranus spinning
on its side
without destroying
the ice giant.
Around four billion years ago,
icy protoplanets
surround a young Uranus.
One ice ball planet, twice the
size of Earth, wanders too close.
The ice giant's immense gravity
locks the planet
into a collision course.
The impact knocks
Uranus backwards
The smaller planet
disintegrates in a shower
of water and methane ice.
The crash leaves Uranus
tilted over permanently.
The icy debris comes together
over time
to form the ice giant's
27 moons,
and a spectacular ring system,
similar to the one around Saturn.
When you think about this
violent destructive collision
that tilted the whole world
on its side,
there was also a creative
flipside to it, as well.
It generated a whole new
system of moons and rings.
Voyager 2 arrives
at Neptune in 1989.
Here it uncovers
another ice giant enigma.
The spacecraft captures this
image of a mysterious cyclone
in Neptune's
southern hemisphere.
It is almost 8,000 miles wide.
There was a
beautiful surprise waiting for us
when Voyager finally
got out to Neptune.
There was a giant storm
churning away in the atmosphere.
This storm was about
the size of the Earth
and we called it the Dark Spot.
The instruments
on board Voyager 2
measured the wind speed
inside this mega-storm
to be in excess
of 1,500 miles per hour.
The winds are moving so fast,
they're moving twice the speed
of a commercial airliner.
When you look at
pictures of Uranus and Neptune,
they're just kinda green
and just kinda blue.
But, in fact, these atmospheres
are incredibly dynamic
with enormous storms
erupting all the time.
The very workings of
Neptune's atmosphere are very mysterious.
How do you form
a huge Earth-size storm
and winds that blow that fast
at that cold temperature?
The Sun powers
the weather on Earth.
Its radiation heats
the surface of our planet.
This heat creates currents
in the atmosphere
that move to make wind.
Neptune is almost three
billion miles away from the Sun.
The energy that Neptune
receives from this star
is too weak to drive its weather
in the same way as on Earth.
So where does the massive energy
that drives these storms come from?
The Hubble Space Telescope
finds a clue
almost 30 years after Voyager 2
discovers the Great Dark Spot.
In 2018,
the telescope captures
this image of a new dark spot.
This one is in the
planet's northern hemisphere.
The amazing thing about Neptune
is how dynamic it is.
We see evidence
of new dark spots forming.
So this world
is very much alive.
It may be cold,
but it's not dead.
Astronomers scour other
images of Neptune taken by Hubble
for clues that can unlock
the genesis of this new spot.
Hubble photographs the surface
of the ice giants every year.
It creates these rolled out two-dimensional
images of the surface of Neptune.
Astronomers use these images to
monitor changes in Neptune's atmosphere.
They see something unusual
in this photograph from 2017.
Mysterious clouds of methane
cover the area
where Hubble sees
the dark spot a year later.
On Earth, storms form when
warm air rises carrying water vapor with it
and that forms bright clouds.
Well, we think a similar thing
is happening on Neptune.
Methane is coming up
through the atmosphere,
rises up and cools and forms these
bright white clouds we see on Neptune,
right before the
big storm erupts.
These clouds are
evidence that it is an energy source
inside Neptune that
drives the dark spot storms.
What is this mysterious
source of energy?
And how does it generate the
fastest winds in the solar system?
The storm winds on Neptune
exceed 1500 miles per hour.
But how can a giant planet
made of ice,
far away from the Sun,
have the energy to drive these
mega-hurricanes?
The very large telescope in Chile
takes infrared images of Neptune
to reveal its temperature.
This heat map shows that the
upper atmosphere of Neptune
is -330 degrees Fahrenheit.
But this frozen ice world
has a core temperature
of 12600 degrees Fahrenheit.
That is hotter than
the surface of the Sun.
Neptune's high core temperature
is the result of the planet's formation
billions of years ago.
The early solar system is a massive
fast-moving disc of gas and dust.
Gravity collapses clouds
of this gas into protoplanets.
The temperature inside a planet
rises as more material
compresses to grow its mass.
Neptune formed from the collapse
of gas and dust under its own gravity.
And that collapse can lock in
a lot of that internal energy
left over from the early days
of the solar system
that can last within the
planet for billions of years.
Astronomers think
that this difference in temperature
between Neptune's hot core
and cold atmosphere
is what triggers the
planet's superstorms.
The extreme heat that radiates
from Neptune's core
vaporizes the frozen gas
close to the planet's surface.
This forces methane gas
high into the coldest parts
of the atmosphere,
where it crystalizes
into wispy clouds.
The hot rising gas beneath
finally erupts.
It punches a hole
in the upper atmosphere
that appears as
a Giant Dark Spot.
The extreme temperature
difference between the gases
generates mega
convection currents
that whip the spot into
a supersonic vortex.
The driving force behind
Neptune's mysterious mega winds
is not the final mystery
the ice giants pose.
Uranus is 14 times
more massive than Earth.
Neptune is a whopping 17 times
more massive.
These huge worlds prowl the
farthest reaches of the solar system
between 1.8 and 3 billion
miles from the Sun.
This strange combination of
supersize and distant position
presents a big puzzle
for astronomers to solve.
One of the mysteries
of Uranus and Neptune
is their location
in the solar system.
They're so far away from the Sun
that there would not
have been enough material
in the early solar system to
build large planets of that size.
It shouldn't be possible for
these guys to exist where they do.
But they do.
The early solar system
is a swirling disc of gas and dust.
When the Sun ignites, its heat
blows away the lighter elements.
Over 400 million miles out,
it is cold enough for these
elements to condense as gas and ice,
and settle in a band
around the Sun.
This material binds together to form
the beginnings of Jupiter and Saturn.
These planets grow larger as they
absorb more and more gas and dust.
But where Neptune
and Uranus orbit,
the raw materials to build
giant planets
are in much shorter supply.
So how is it possible for the
ice giants to form this far out?
To build a planet,
especially a giant one,
we need countless tiny
rocky and icy bodies
to come together,
to grow over time.
And we think that where we see
these planets nowadays,
in the far outskirts
of our solar system,
this material was
just too scarce
to grow planets that large.
Astronomers arrive
at an astonishing conclusion
to explain this anomaly.
The ice giants come from
somewhere else in the solar system.
One possible solution is that
Uranus and Neptune didn't form
where they are now.
If they formed
closer into the Sun,
there would have been
enough material
to create such large planets.
And then somehow, Uranus and
Neptune moved out to where they are today.
Why did these ice giants migrate
to the farthest reaches
of the solar system?
And what was the role of these planets
in shaping the solar system we see today?
Astronomers think that
Neptune and Uranus
were not born in the far
reaches of the solar system,
where they are today.
Instead, they formed
closer to the Sun
and then moved
farther and farther out.
What triggered this epic
migration of the ice giants?
Scientists believe the answer
is locked inside meteorites.
Meteorites are the parts of ancient
asteroids that collide with Earth.
They contain tiny quantities
of radioactive elements.
These elements allow
scientists to date the meteorites,
to discover the exact age of
the asteroids they come from.
Meteorites that fall to Earth
have elements like uranium,
which is radioactive.
And this radioactive decay
that uranium undergoes
is like a ticking clock
that allows us to get
the age of the meteorite.
The radioactive
clock starts ticking
when the space rock first forms
at the birth of the solar system.
That means all meteorites should
be around 4.6 billion years old.
But scientists make
an extraordinary discovery
when they date the space rocks
that fall to Earth.
One that can unlock the
mystery of why the ice giants
moved farther out
across the solar system.
When we get the ages of
meteorites through radioactive decay,
we find that most of them are about
the same age as the solar system itself.
However, a lot of meteorites
have a significantly younger age.
The clocks of
these younger asteroids
start ticking around 80 million
years after the solar system forms.
Super-heating and melting
the minerals inside asteroids
resets their radioactive clocks.
Scientists believe that
only a super-violent
solar system-wide catastrophe
could generate
temperatures high enough
to melt down so much rock.
We're talking destruction
on a truly unprecedented scale.
Entire worlds colliding
together and getting obliterated,
asteroids flying
every which way you look.
If you were to actually look
up in the sky during this time,
you'd have seen this destructive
light show unlike any other.
Objects were streaming around,
smashing into each other,
and remelting.
And that's why these meteorites
seem to be younger than
the solar system itself.
Scientists think this disaster
impacts all the planets
in the solar system...
including the ice giants.
But what triggers
this mega violent event?
And how does it banish
Uranus and Neptune
to a region of space billions
of miles from the Sun?
Astronomers believed that
the proximity of the ice giants
to their gas giant neighbors,
Jupiter and Saturn,
unlocks the mystery.
Probably all four
major worlds of our solar system,
Jupiter, Saturn,
Uranus and Neptune
were competing for
planet-building materials,
jockeying for position
in a young solar system.
All of a sudden, you're kind
of playing planetary pinball.
Around
4.6 billion years ago,
Jupiter, Saturn,
Neptune and Uranus
orbit much closer to each
other than they do today.
Back then, their proximity
causes gravitational chaos.
The huge gravity of
the larger Jupiter and Saturn
forces out
the smaller ice giants.
And they begin an epic journey
across the solar system.
One theory is that they even
swap places along the way.
Uranus and Neptune
travel billions of miles
to end up in the sparse outer
reaches of the solar system.
The truth of the matter is that
if you're jostling with Jupiter
and Saturn for real estate,
even an ice giant
really doesn't stand
much of a chance.
It's out to the suburbs.
This gravitational battle
between Jupiter, Saturn
and the ice giants
triggers an intense asteroid
bombardment on the solar system.
Space rocks smash together
in mega impacts
in the most violent period
of the solar system's history.
This stress melts and reforms
the asteroids,
and resets their
radioactive clocks.
Over time, many of these rocks
drift into
the inner solar system
and crashed to Earth
as meteorites.
The migration of
Uranus and Neptune
explains why the ice giants
orbit so far from the Sun.
Their movement reshuffles
the entire solar system.
And locks it into the
configuration we know today.
The ice giants are the weirdest
worlds in the solar system.
From Neptune's
superfast winds...
and the giant geysers
on its moon, Triton...
to the bizarre sideways
rotation of Uranus...
and it's strange magnetic field
powered by
an exotic form of water...
these two planets
break all the rules.
Uranus and Neptune
are dynamic, interesting,
and above all else,
weird places.
The ice giants prove to us that
there's no such thing
as a normal planet.
They work in
an entirely different way
than any other type of planet
that we know of.
They just completely
blow away our ideas
of how planets are formed.
So far, we only had a glimpse
of these ice giant planets.
And the next probes
that go there,
might find they're even weirder
than we think now.
Our solar system
would be a very different place,
if it were not for these
strange oddball worlds.
Two of the largest,
farthest
and strangest planets
in our solar system.
Of all the big planets,
Uranus and Neptune
remain the biggest enigmas.
Today, astronomers
are finally unlocking
why these supersized snowballs
are so weird.
In Uranus
and Neptune, we have two planets
that just don't like
playing by the rules.
Can an ancient mega-collision
reveal what knocked
Uranus onto its side?
Can a missing twin world
unlock why one of Neptune's
moons orbits the wrong way?
This is a large moon
but yet it's orbiting
the planet backwards.
That's a mystery that
needs explaining.
And what is the
energy that drives the fastest winds
in the solar system?
It's a rare planet that has winds
faster than the speed of sound.
To find out, we
venture to these frozen planets
explore their alien underworlds
to reveal what makes
these ice giants
the weirdest worlds
in the solar system.
At the limits of our
solar system lie two huge planets.
Uranus
and Neptune.
Both are over 14 times
the mass of Earth.
They orbit more than 2.8
billion miles away from the Sun.
This makes them the farthest out,
confirmed planets in the solar system.
And the most mysterious.
We have sent orbiters
to every major planet
in the solar system
except Uranus and Neptune.
Uranus and Neptune
are really far away
and sending a space probe
out there is pretty hard.
Only one NASA mission
has ventured out
for a closer look.
Voyager 2 flies past Uranus
in 1986
and Neptune in 1989.
The spacecraft reveals
that these planets,
sculpted from frozen water,
methane and ammonium,
are far from dead.
The thing that's
so poignant about the ice giant worlds,
is that we've only visited them
for a couple of days.
The Voyager spacecraft
just flew on by.
And yet,
in that brief encounter,
we saw things we never expected.
Instead of cold, boring worlds
like we maybe
thought they would be,
they were exciting.
They had weather.
They turned out to be much more
dynamic than we ever imagined.
As Voyager 2 flies by,
it captures
detailed photographs,
of the strange moons
that orbit the ice giants.
Uranus has 27 moons.
Neptune has 14.
The ice giants have
some of the most fascinating
moons in the solar system.
You have Naiad and Thalassa,
two moons of Neptune
that are locked
in this gravitational dance
with one another.
And they zig-zag up and down
unlike any other moons
in the solar system.
Uranus has Miranda,
this moon that seems to have
been cracked apart and reassembled,
with vast craters and
giant cliffs and fields of ice.
The weirdest moon
of all is Triton.
Triton is around half the size
of Earth's moon.
But it is 400 times more massive than
Neptune's next largest moon, Proteus.
Two-thirds
of Triton is rock and metal.
The rest is a crust of water
and nitrogen ice,
frozen to a temperature of
minus 390 degrees Fahrenheit.
This ice world is unlike any other
large moon in the solar system.
Triton is really unique
in that it's the only large
moon in the solar system
with a retrograde orbit.
That's an orbit that is opposite to
the direction of the planet's spin.
Scientists think that
most planets and their moons
form from the same
spinning cloud of gas and dust.
The center of the spinning cloud
collapses to form
a rotating planet
while the outer edge condenses
into the planet's moons.
Everything turns
in the same direction
as the original cloud.
So, how does Triton end up
orbiting Neptune in reverse?
Today, new technologies
and discoveries
make it possible
to finally unlock
the mysteries of the ice giants.
A clue about Triton's
strange orbit
lies in the data collected by one
of NASA's most ambitious missions
to the outer solar system.
In 2015,
NASA's New Horizons probe
flies past Pluto.
Pluto is a dwarf planet.
It is the largest object
in the Kuiper belt,
a massive ring
of billions of space rocks
that lies beyond
the orbit of Neptune,
on the fringes
of the solar system.
New Horizons beams back to Earth
breathtaking images
of this frozen world.
Pluto just blew me away.
We saw glaciers
made of nitrogen ice.
And one of my favorite images
from the past decade
is sunlight glinting off of
mountains of pure water ice.
The scientific
instruments on board the probe
analyzed Pluto's
vital statistics
to unlock what the
dwarf planet is made from.
The instruments revealed
that Pluto and Triton
are almost exactly the same.
The bodies are roughly
the same size.
Both Pluto and Triton have
cores made from rock and metal.
And their crusts consist of layers of
frozen nitrogen, water and methane.
This evidence points to
an incredible possibility.
One that could solve the mystery
of why Triton
orbits Neptune backwards.
Triton and Pluto
are in many ways
geological twins.
One of the simplest explanations
that could account for that
is that they originated
from the same place.
That place is the Kuiper Belt.
Why did Triton break out
from this ring of rocks?
Astronomers think that
Neptune's size
could reveal the answer.
Neptune is 17 times
more massive than Earth.
This mass gives the planet
a super-strong
gravitational influence.
It is possible that over time
Neptune's huge gravity
gradually pulls Triton away
from this ring of rocks
to eventually capture it
as its moon.
But there is one problem
with this theory:
the speed of the objects
inside the Kuiper Belt.
If you do the
calculations what you will find is,
by the time a solitary Triton
passes by Neptune,
it's moving too fast
to be captured.
Neptune's gravity would
have deflected it,
but it would have
just kept on going.
In order for Triton to end up
in orbit around Neptune,
something would have had to
hit the brakes and slowed it down.
What slowed down Triton enough
for Neptune to capture it?
And how did this dwarf planet
end up orbiting
Neptune backwards?
The giant ice planet, Neptune,
has a weird moon.
Triton orbits
in the opposite direction
to Neptune's rotation.
One explanation is that
the planet pulled Triton
from the Kuiper Belt.
But what slowed down
Triton enough
to allow Neptune to capture it
travelling the wrong way?
Astronomers believe
that one of Pluto's moons
offers a clue.
Charon is half
the size of Pluto.
This closeness in size
makes the pair
dance around each other
as they orbit the sun.
Pluto is not much bigger
like all the other
planets and moons.
So instead of being like,
a single large body
with a smaller one orbiting it,
it's more like a dumbbell,
and this dumbbell
orbits as one thing.
Astronomers call two
orbiting bodies of a similar size
a binary system.
The strange orbit of binaries
could unlock how Triton
slows down enough
for Neptune to capture it
travelling the wrong way.
When objects in the
Kuiper Belt pick up a partner,
they completely change
the way they move
through the cosmos.
Once they've caught each other,
they start revolving around
their common center of gravity.
This disrupts their trajectory,
as on every turn,
one partner must move backwards
against their orbit.
Once every pirouette,
they can slow down so much
that they become vulnerable
to capture.
Some astronomers believe that
Triton once had
its own binary partner,
just like Pluto
has Charon today.
They think that
this missing binary
is the key that unlocks
how Neptune captures Triton.
The discovery that
ten to fifteen percent of
Kuiper Belt objects are binary
may solve the Triton problem.
If Triton itself was a binary,
it had a large companion
when it passed by Neptune.
That could have put
the brakes on it
and allowed it to orbit Neptune.
Triton and its companion
orbit each other
inside the Kuiper Belt.
Over time,
Neptune's gravity
gradually pulls
the pair away from the Belt.
They fall towards
the giant planet
and slingshot around it.
Thanks to their binary dance,
there is a point when
Triton moves slowly enough
for Neptune to capture it.
This breaks the
gravitational bond
between Triton and its partner
and hurls its companion
across the solar system.
Triton is left alone
orbiting Neptune the wrong way.
This companion was kind of
a sacrificial lamb
that got kicked out
into the depths of space
in order for Triton itself to be
captured into Neptune's orbit.
Triton's strange orbit
is just one of this
weird moon's mysteries.
Voyager 2
photographs Triton up-close
in 1989.
The camera on board
captures something weird
on the surface
of this strange world.
Hidden in this grainy photograph
is a mysterious plume
that rises from
the surface of Triton.
The plume is a geyser
of frozen nitrogen
five miles high.
Winds in the moon's
thin upper atmosphere
blow the vapor into trails
that are hundreds of miles long.
When Voyager flew past Triton,
it saw the unexpected.
There were jets of gas shooting
out from the moon's surface.
No one expected that.
It's out at the far reaches
of the solar system.
We expected to find
a cold, dead moon.
What the heck is going on?
Why do geysers
blast from the surface of Triton?
And what is the power source
that drives them?
In 2019,
investigators used the
Gemini South telescope in Chile
to study Triton's icy crust.
Researchers discovered that
the ice on the surface of Triton
is a special cocktail
of carbon monoxide
and frozen nitrogen.
In some ways
you can think of Triton
as having a frozen atmosphere.
Our atmosphere on Earth
is mostly nitrogen
and that's true on Triton too.
But the nitrogen's frozen
into a layer of ice.
That ice is actually
transparent to light.
So, sunlight can get through
that transparent ice
and heat up
little pockets in it.
Some types of ice
transform directly
from a solid into gas,
when they heat up
inside an atmosphere
that is super thin.
Astronomers believe that
this volatility of Triton's ice
unlocks they mystery
of its mega geysers.
At a point in Neptune's year,
Triton's north pole
leans towards the Sun.
This gives one hemisphere
of the moon
a summer that lasts
41 Earth years.
The rays from the Sun are weak
but they can pass through
Triton's nitrogen ice.
Here, they hit
a dark layer of dust
which heats up
by just a few degrees.
Enough to turn the ice above
into gas.
The pressure rises
as the gas builds up,
until it erupts as
powerful geysers of nitrogen.
Voyager 2 shows that ice
giants contain many secrets.
The data it beams back to Earth
reveals another mystery
for astronomers to solve.
The magnetometer
on board the probe
detects that
the magnetic field of Uranus
is super strange.
The field lines
continually twist and shift.
The magnetic poles are offset
from the planet's
axis of rotation
by a massive 60 degrees.
Voyager 2 discovers later
that the magnetic field
of Neptune
is also irregular
and misaligned.
When you think about
the magnetic of a planet,
sometimes you get something
very simple, like the Earth.
It's almost as if
there's a giant bar magnet
going right through
the core of our planet
with a very clear
north pole and south pole.
With the ice giant,
something altogether different
is going on.
The magnetic fields are chaotic.
The magnetic field lines
twist and turn
like a bag of writing snakes.
And the south pole of the planet
is actually along the equator.
Why are the magnetic
fields of the ice giants twisted?
Can a strange material
deep inside Uranus
unlock the mystery?
Uranus and Neptune
lie at the farthest reaches
of our solar system.
Voyager 2 remains
the only mission
to visit these
ice giant planets.
The spacecraft discovers
that they have strange moons
and bizarre,
twisted magnetic fields.
Why are the magnetic fields of
Uranus and Neptune so chaotic?
Scientists believe
the answer lies
in discovering what
inside the ice giants
generates their magnetic fields?
A mass of molten iron and nickel
sits at the center
of a rocky planet like Earth.
This super dense liquid metal
forms a thick and compact shell
wrapped around
the planet's core.
Heat drives powerful currents
inside this concentration
of molten material.
These deep currents
generate a magnetic field.
The rotation of Earth
twists the currents
into orderly streams that
move in the same direction
as Earth turns.
The result is that the axis
of Earth's magnetic field
almost matches the axis
of the planet's rotation.
Well, the magnetic field
is generated
by rotating liquids
inside the planet
and those liquids
are going to rotate
along with the planet itself.
So, it makes sense that
the planet's geographic
north and south pole
align with the magnetic
north and south pole.
However, with Uranus,
we don't see that.
An ice giant
contains no moving metal
at its core.
Scientists believe
the cores of these planets
are made from a mixture of
rock, water,
methane and ammonia.
So, what happens at
the center of ice giants?
Scientists at the University
of Rochester in New York
believe that the huge pressure
at the core of ice giants
helps unlock the mystery.
In 2018,
they test how this pressure
transforms water
into weird states of matter
with strange properties.
They use an anvil
made of diamonds
to compress a sample of water
to a pressure similar to that
at the core of an ice giant.
The crust water transforms
at the molecular level
and turns into a super-hot
jet black material
called superionic ice.
Its oxygen atoms
form a rigid lattice
that hydrogen atoms
can float through,
meaning that it can become
electrically charged.
But this weird ice is rigid.
So if it is at the core
of the ice giants
it creates
a fundamental problem.
Only moving material
inside a planet
can act like a dynamo
and generate a magnetic field.
The Rochester experiment
shows that an ice giant's core
could be static.
This means that
the planet's magnetic field
can't come from there.
Water ice
under the right conditions
very compressed
to the core of a planet
is actually stopping
the magnetic field
going through the very center
of the planet.
So there's gonna be
no magnetic field
based in the core of Uranus.
If the super pressurized
ice core of an ice giant
doesn't generate
the planet's magnetic field,
then what does?
One theory is that a liquid
ocean of compressed water
exists in a thin shell
around the solid core
of an ice giant.
Farther up from the core,
there's this sort of
a Goldilocks Zone.
Not too compressed,
the water can flow around
yet still be
electrically charged,
and there's your magnetic field.
How this layer
of pressurized liquid
moves around this solid
superionic ice core,
could unlock why
the magnetic fields
of ice giants are chaotic.
Deep inside Uranus...
...lies a compressed
superionic ice core
that is a scorching
9,000 degrees Fahrenheit.
Somewhere in between
this rigid ball
and the surface of the planet
is a shell of highly
pressurized water that can flow.
But the disconnected currents
inside this layer
do not generate
a magnetic field that matches
the direction
of the planet's rotation.
So that's how the magnetic
fields of the ice giants
can slip and become misaligned.
Weird water unlocks
why the ice giants
have super strange
magnetic fields.
But these mega planets
contain more mysteries
for astronomers to solve.
Voyager 2 sees up close, arguably,
the single strangest characteristic
of either of these
distant planets.
There's a lot of
weird stuff about Uranus
but maybe the weirdest is
that it orbits the Sun on its side.
Uranus leans over
98 degrees from the vertical.
It is the only planet
in the solar system
that is orientated this way.
Why does this ice giant
roll around the Sun
like a huge beach ball?
Astronomers think
that planets form
from a disc of gas and dust...
orbiting a young star.
These young worlds inherit both
their direction and axes of spin
from the angle of the disc.
This means that
all of the planets
should be born with a spin axis
that is roughly
90 degrees to the disc.
This model predicts that
Uranus starts life upright,
just like all the other
planets in the solar system.
So what tips Uranus
onto its side after it forms?
Scientists believe that a clue lies
in our solar system's violent past.
The early days
of the solar system
were a chaotic maelstrom
of smash-and-grabs.
We see evidence of this, of
course, in the form of craters
on many bodies
in the solar system.
Does an ancient
mega-collision knock Uranus onto its side?
And what are the mysterious
spots in the atmosphere of Neptune?
Uranus leans over so
much that it orbits the Sun on its side.
One explanation is that
Uranus is involved
in a mega-collision
billions of years ago.
But what kind of cosmic crash
can knock over an entire planet?
Researchers at the University
of Durham in the United Kingdom
simulate impacts between
Uranus and large protoplanets.
They build a virtual Uranus
and fire space objects at it
from different angles.
These simulations show
that a head-on collision
blows apart the virtual Uranus.
But a sideswipe generates
just the right amount of force
to leave Uranus spinning
on its side
without destroying
the ice giant.
Around four billion years ago,
icy protoplanets
surround a young Uranus.
One ice ball planet, twice the
size of Earth, wanders too close.
The ice giant's immense gravity
locks the planet
into a collision course.
The impact knocks
Uranus backwards
The smaller planet
disintegrates in a shower
of water and methane ice.
The crash leaves Uranus
tilted over permanently.
The icy debris comes together
over time
to form the ice giant's
27 moons,
and a spectacular ring system,
similar to the one around Saturn.
When you think about this
violent destructive collision
that tilted the whole world
on its side,
there was also a creative
flipside to it, as well.
It generated a whole new
system of moons and rings.
Voyager 2 arrives
at Neptune in 1989.
Here it uncovers
another ice giant enigma.
The spacecraft captures this
image of a mysterious cyclone
in Neptune's
southern hemisphere.
It is almost 8,000 miles wide.
There was a
beautiful surprise waiting for us
when Voyager finally
got out to Neptune.
There was a giant storm
churning away in the atmosphere.
This storm was about
the size of the Earth
and we called it the Dark Spot.
The instruments
on board Voyager 2
measured the wind speed
inside this mega-storm
to be in excess
of 1,500 miles per hour.
The winds are moving so fast,
they're moving twice the speed
of a commercial airliner.
When you look at
pictures of Uranus and Neptune,
they're just kinda green
and just kinda blue.
But, in fact, these atmospheres
are incredibly dynamic
with enormous storms
erupting all the time.
The very workings of
Neptune's atmosphere are very mysterious.
How do you form
a huge Earth-size storm
and winds that blow that fast
at that cold temperature?
The Sun powers
the weather on Earth.
Its radiation heats
the surface of our planet.
This heat creates currents
in the atmosphere
that move to make wind.
Neptune is almost three
billion miles away from the Sun.
The energy that Neptune
receives from this star
is too weak to drive its weather
in the same way as on Earth.
So where does the massive energy
that drives these storms come from?
The Hubble Space Telescope
finds a clue
almost 30 years after Voyager 2
discovers the Great Dark Spot.
In 2018,
the telescope captures
this image of a new dark spot.
This one is in the
planet's northern hemisphere.
The amazing thing about Neptune
is how dynamic it is.
We see evidence
of new dark spots forming.
So this world
is very much alive.
It may be cold,
but it's not dead.
Astronomers scour other
images of Neptune taken by Hubble
for clues that can unlock
the genesis of this new spot.
Hubble photographs the surface
of the ice giants every year.
It creates these rolled out two-dimensional
images of the surface of Neptune.
Astronomers use these images to
monitor changes in Neptune's atmosphere.
They see something unusual
in this photograph from 2017.
Mysterious clouds of methane
cover the area
where Hubble sees
the dark spot a year later.
On Earth, storms form when
warm air rises carrying water vapor with it
and that forms bright clouds.
Well, we think a similar thing
is happening on Neptune.
Methane is coming up
through the atmosphere,
rises up and cools and forms these
bright white clouds we see on Neptune,
right before the
big storm erupts.
These clouds are
evidence that it is an energy source
inside Neptune that
drives the dark spot storms.
What is this mysterious
source of energy?
And how does it generate the
fastest winds in the solar system?
The storm winds on Neptune
exceed 1500 miles per hour.
But how can a giant planet
made of ice,
far away from the Sun,
have the energy to drive these
mega-hurricanes?
The very large telescope in Chile
takes infrared images of Neptune
to reveal its temperature.
This heat map shows that the
upper atmosphere of Neptune
is -330 degrees Fahrenheit.
But this frozen ice world
has a core temperature
of 12600 degrees Fahrenheit.
That is hotter than
the surface of the Sun.
Neptune's high core temperature
is the result of the planet's formation
billions of years ago.
The early solar system is a massive
fast-moving disc of gas and dust.
Gravity collapses clouds
of this gas into protoplanets.
The temperature inside a planet
rises as more material
compresses to grow its mass.
Neptune formed from the collapse
of gas and dust under its own gravity.
And that collapse can lock in
a lot of that internal energy
left over from the early days
of the solar system
that can last within the
planet for billions of years.
Astronomers think
that this difference in temperature
between Neptune's hot core
and cold atmosphere
is what triggers the
planet's superstorms.
The extreme heat that radiates
from Neptune's core
vaporizes the frozen gas
close to the planet's surface.
This forces methane gas
high into the coldest parts
of the atmosphere,
where it crystalizes
into wispy clouds.
The hot rising gas beneath
finally erupts.
It punches a hole
in the upper atmosphere
that appears as
a Giant Dark Spot.
The extreme temperature
difference between the gases
generates mega
convection currents
that whip the spot into
a supersonic vortex.
The driving force behind
Neptune's mysterious mega winds
is not the final mystery
the ice giants pose.
Uranus is 14 times
more massive than Earth.
Neptune is a whopping 17 times
more massive.
These huge worlds prowl the
farthest reaches of the solar system
between 1.8 and 3 billion
miles from the Sun.
This strange combination of
supersize and distant position
presents a big puzzle
for astronomers to solve.
One of the mysteries
of Uranus and Neptune
is their location
in the solar system.
They're so far away from the Sun
that there would not
have been enough material
in the early solar system to
build large planets of that size.
It shouldn't be possible for
these guys to exist where they do.
But they do.
The early solar system
is a swirling disc of gas and dust.
When the Sun ignites, its heat
blows away the lighter elements.
Over 400 million miles out,
it is cold enough for these
elements to condense as gas and ice,
and settle in a band
around the Sun.
This material binds together to form
the beginnings of Jupiter and Saturn.
These planets grow larger as they
absorb more and more gas and dust.
But where Neptune
and Uranus orbit,
the raw materials to build
giant planets
are in much shorter supply.
So how is it possible for the
ice giants to form this far out?
To build a planet,
especially a giant one,
we need countless tiny
rocky and icy bodies
to come together,
to grow over time.
And we think that where we see
these planets nowadays,
in the far outskirts
of our solar system,
this material was
just too scarce
to grow planets that large.
Astronomers arrive
at an astonishing conclusion
to explain this anomaly.
The ice giants come from
somewhere else in the solar system.
One possible solution is that
Uranus and Neptune didn't form
where they are now.
If they formed
closer into the Sun,
there would have been
enough material
to create such large planets.
And then somehow, Uranus and
Neptune moved out to where they are today.
Why did these ice giants migrate
to the farthest reaches
of the solar system?
And what was the role of these planets
in shaping the solar system we see today?
Astronomers think that
Neptune and Uranus
were not born in the far
reaches of the solar system,
where they are today.
Instead, they formed
closer to the Sun
and then moved
farther and farther out.
What triggered this epic
migration of the ice giants?
Scientists believe the answer
is locked inside meteorites.
Meteorites are the parts of ancient
asteroids that collide with Earth.
They contain tiny quantities
of radioactive elements.
These elements allow
scientists to date the meteorites,
to discover the exact age of
the asteroids they come from.
Meteorites that fall to Earth
have elements like uranium,
which is radioactive.
And this radioactive decay
that uranium undergoes
is like a ticking clock
that allows us to get
the age of the meteorite.
The radioactive
clock starts ticking
when the space rock first forms
at the birth of the solar system.
That means all meteorites should
be around 4.6 billion years old.
But scientists make
an extraordinary discovery
when they date the space rocks
that fall to Earth.
One that can unlock the
mystery of why the ice giants
moved farther out
across the solar system.
When we get the ages of
meteorites through radioactive decay,
we find that most of them are about
the same age as the solar system itself.
However, a lot of meteorites
have a significantly younger age.
The clocks of
these younger asteroids
start ticking around 80 million
years after the solar system forms.
Super-heating and melting
the minerals inside asteroids
resets their radioactive clocks.
Scientists believe that
only a super-violent
solar system-wide catastrophe
could generate
temperatures high enough
to melt down so much rock.
We're talking destruction
on a truly unprecedented scale.
Entire worlds colliding
together and getting obliterated,
asteroids flying
every which way you look.
If you were to actually look
up in the sky during this time,
you'd have seen this destructive
light show unlike any other.
Objects were streaming around,
smashing into each other,
and remelting.
And that's why these meteorites
seem to be younger than
the solar system itself.
Scientists think this disaster
impacts all the planets
in the solar system...
including the ice giants.
But what triggers
this mega violent event?
And how does it banish
Uranus and Neptune
to a region of space billions
of miles from the Sun?
Astronomers believed that
the proximity of the ice giants
to their gas giant neighbors,
Jupiter and Saturn,
unlocks the mystery.
Probably all four
major worlds of our solar system,
Jupiter, Saturn,
Uranus and Neptune
were competing for
planet-building materials,
jockeying for position
in a young solar system.
All of a sudden, you're kind
of playing planetary pinball.
Around
4.6 billion years ago,
Jupiter, Saturn,
Neptune and Uranus
orbit much closer to each
other than they do today.
Back then, their proximity
causes gravitational chaos.
The huge gravity of
the larger Jupiter and Saturn
forces out
the smaller ice giants.
And they begin an epic journey
across the solar system.
One theory is that they even
swap places along the way.
Uranus and Neptune
travel billions of miles
to end up in the sparse outer
reaches of the solar system.
The truth of the matter is that
if you're jostling with Jupiter
and Saturn for real estate,
even an ice giant
really doesn't stand
much of a chance.
It's out to the suburbs.
This gravitational battle
between Jupiter, Saturn
and the ice giants
triggers an intense asteroid
bombardment on the solar system.
Space rocks smash together
in mega impacts
in the most violent period
of the solar system's history.
This stress melts and reforms
the asteroids,
and resets their
radioactive clocks.
Over time, many of these rocks
drift into
the inner solar system
and crashed to Earth
as meteorites.
The migration of
Uranus and Neptune
explains why the ice giants
orbit so far from the Sun.
Their movement reshuffles
the entire solar system.
And locks it into the
configuration we know today.
The ice giants are the weirdest
worlds in the solar system.
From Neptune's
superfast winds...
and the giant geysers
on its moon, Triton...
to the bizarre sideways
rotation of Uranus...
and it's strange magnetic field
powered by
an exotic form of water...
these two planets
break all the rules.
Uranus and Neptune
are dynamic, interesting,
and above all else,
weird places.
The ice giants prove to us that
there's no such thing
as a normal planet.
They work in
an entirely different way
than any other type of planet
that we know of.
They just completely
blow away our ideas
of how planets are formed.
So far, we only had a glimpse
of these ice giant planets.
And the next probes
that go there,
might find they're even weirder
than we think now.
Our solar system
would be a very different place,
if it were not for these
strange oddball worlds.