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[narrator] Uranus and Neptune.
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00:00:04,270 --> 00:00:06,071
Two of the largest,
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farthest
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and strangest planets
in our solar system.
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[Phil Plait]
Of all the big planets,
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Uranus and Neptune
remain the biggest enigmas.
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[narrator] Today, astronomers
are finally unlocking
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why these supersized snowballs
are so weird.
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[Grant Tremblay] In Uranus
and Neptune, we have two planets
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that just don't like
playing by the rules.
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[narrator] Can an
ancient mega-collision
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reveal what knocked
Uranus onto its side?
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Can a missing twin world
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unlock why one of Neptune's
moons orbits the wrong way?
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[Hakeem Oluseyi]
This is a large moon
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but yet it's orbiting
the planet backwards.
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That's a mystery that
needs explaining.
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[narrator] And what is the
energy that drives the fastest winds
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in the solar system?
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It's a rare planet that has winds
faster than the speed of sound.
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[narrator] To find out, we
venture to these frozen planets
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explore their alien underworlds
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to reveal what makes
these ice giants
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the weirdest worlds
in the solar system.
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[narrator] At the limits of our
solar system lie two huge planets.
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Uranus
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and Neptune.
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Both are over 14 times
the mass of Earth.
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They orbit more than 2.8
billion miles away from the Sun.
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This makes them the farthest out,
confirmed planets in the solar system.
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And the most mysterious.
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We have sent orbiters
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to every major planet
in the solar system
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except Uranus and Neptune.
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Uranus and Neptune
are really far away
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and sending a space probe
out there is pretty hard.
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[beeping]
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[narrator] Only one NASA mission
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has ventured out
for a closer look.
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Voyager 2 flies past Uranus
in 1986
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and Neptune in 1989.
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The spacecraft reveals
that these planets,
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sculpted from frozen water,
methane and ammonium,
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are far from dead.
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[Michelle Thaller] The thing that's
so poignant about the ice giant worlds,
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is that we've only visited them
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for a couple of days.
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The Voyager spacecraft
just flew on by.
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And yet,
in that brief encounter,
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we saw things we never expected.
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Instead of cold, boring worlds
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like we maybe
thought they would be,
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they were exciting.
They had weather.
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They turned out to be much more
dynamic than we ever imagined.
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[beeping]
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[narrator]
As Voyager 2 flies by,
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it captures
detailed photographs,
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of the strange moons
that orbit the ice giants.
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Uranus has 27 moons.
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Neptune has 14.
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[Tremblay] The ice giants have
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some of the most fascinating
moons in the solar system.
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You have Naiad and Thalassa,
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two moons of Neptune
that are locked
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in this gravitational dance
with one another.
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And they zig-zag up and down
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unlike any other moons
in the solar system.
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[Thaller] Uranus has Miranda,
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this moon that seems to have
been cracked apart and reassembled,
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with vast craters and
giant cliffs and fields of ice.
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[narrator] The weirdest moon
of all is Triton.
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Triton is around half the size
of Earth's moon.
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But it is 400 times more massive than
Neptune's next largest moon, Proteus.
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[narrator] Two-thirds
of Triton is rock and metal.
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The rest is a crust of water
and nitrogen ice,
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frozen to a temperature of
minus 390 degrees Fahrenheit.
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This ice world is unlike any other
large moon in the solar system.
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[Tremblay]
Triton is really unique
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in that it's the only large
moon in the solar system
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with a retrograde orbit.
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That's an orbit that is opposite to
the direction of the planet's spin.
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[narrator] Scientists think that
most planets and their moons
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form from the same
spinning cloud of gas and dust.
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The center of the spinning cloud
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collapses to form
a rotating planet
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while the outer edge condenses
into the planet's moons.
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Everything turns
in the same direction
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as the original cloud.
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So, how does Triton end up
orbiting Neptune in reverse?
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Today, new technologies
and discoveries
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make it possible
to finally unlock
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the mysteries of the ice giants.
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A clue about Triton's
strange orbit
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lies in the data collected by one
of NASA's most ambitious missions
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to the outer solar system.
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In 2015,
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NASA's New Horizons probe
flies past Pluto.
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Pluto is a dwarf planet.
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It is the largest object
in the Kuiper belt,
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a massive ring
of billions of space rocks
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that lies beyond
the orbit of Neptune,
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on the fringes
of the solar system.
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New Horizons beams back to Earth
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breathtaking images
of this frozen world.
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Pluto just blew me away.
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We saw glaciers
made of nitrogen ice.
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And one of my favorite images
from the past decade
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is sunlight glinting off of
mountains of pure water ice.
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[narrator] The scientific
instruments on board the probe
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analyzed Pluto's
vital statistics
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to unlock what the
dwarf planet is made from.
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The instruments revealed
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that Pluto and Triton
are almost exactly the same.
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The bodies are roughly
the same size.
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Both Pluto and Triton have
cores made from rock and metal.
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And their crusts consist of layers of
frozen nitrogen, water and methane.
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This evidence points to
an incredible possibility.
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One that could solve the mystery
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of why Triton
orbits Neptune backwards.
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[Tremblay] Triton and Pluto
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are in many ways
geological twins.
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One of the simplest explanations
that could account for that
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is that they originated
from the same place.
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[narrator] That place
is the Kuiper Belt.
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Why did Triton break out
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from this ring of rocks?
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Astronomers think that
Neptune's size
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could reveal the answer.
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Neptune is 17 times
more massive than Earth.
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This mass gives the planet
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a super-strong
gravitational influence.
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It is possible that over time
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Neptune's huge gravity
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gradually pulls Triton away
from this ring of rocks
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to eventually capture it
as its moon.
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But there is one problem
with this theory:
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the speed of the objects
inside the Kuiper Belt.
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[Oluseyi] If you do the
calculations what you will find is,
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by the time a solitary Triton
passes by Neptune,
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it's moving too fast
to be captured.
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Neptune's gravity would
have deflected it,
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but it would have
just kept on going.
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In order for Triton to end up
in orbit around Neptune,
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something would have had to
hit the brakes and slowed it down.
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[narrator] What slowed down
Triton enough
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for Neptune to capture it?
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And how did this dwarf planet
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end up orbiting
Neptune backwards?
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[narrator] The giant
ice planet, Neptune,
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has a weird moon.
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Triton orbits
in the opposite direction
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to Neptune's rotation.
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One explanation is that
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the planet pulled Triton
from the Kuiper Belt.
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But what slowed down
Triton enough
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to allow Neptune to capture it
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travelling the wrong way?
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Astronomers believe
that one of Pluto's moons
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offers a clue.
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Charon is half
the size of Pluto.
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This closeness in size
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makes the pair
dance around each other
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as they orbit the sun.
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[Oluseyi] Pluto
is not much bigger
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like all the other
planets and moons.
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So instead of being like,
a single large body
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with a smaller one orbiting it,
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it's more like a dumbbell,
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and this dumbbell
orbits as one thing.
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[narrator] Astronomers call two
orbiting bodies of a similar size
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a binary system.
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The strange orbit of binaries
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could unlock how Triton
slows down enough
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for Neptune to capture it
travelling the wrong way.
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When objects in the
Kuiper Belt pick up a partner,
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they completely change
the way they move
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through the cosmos.
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Once they've caught each other,
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they start revolving around
their common center of gravity.
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This disrupts their trajectory,
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as on every turn,
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one partner must move backwards
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against their orbit.
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Once every pirouette,
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they can slow down so much
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that they become vulnerable
to capture.
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Some astronomers believe that
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Triton once had
its own binary partner,
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just like Pluto
has Charon today.
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They think that
this missing binary
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is the key that unlocks
how Neptune captures Triton.
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[Plait] The discovery that
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ten to fifteen percent of
Kuiper Belt objects are binary
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may solve the Triton problem.
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If Triton itself was a binary,
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it had a large companion
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when it passed by Neptune.
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That could have put
the brakes on it
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and allowed it to orbit Neptune.
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[narrator]
Triton and its companion
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00:11:07,466 --> 00:11:09,734
orbit each other
inside the Kuiper Belt.
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00:11:11,303 --> 00:11:12,470
Over time,
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Neptune's gravity
gradually pulls
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00:11:14,473 --> 00:11:16,441
the pair away from the Belt.
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They fall towards
the giant planet
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00:11:19,745 --> 00:11:21,579
and slingshot around it.
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00:11:22,348 --> 00:11:24,482
Thanks to their binary dance,
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00:11:24,517 --> 00:11:27,252
there is a point when
Triton moves slowly enough
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for Neptune to capture it.
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00:11:31,557 --> 00:11:33,258
This breaks the
gravitational bond
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00:11:33,292 --> 00:11:36,394
between Triton and its partner
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00:11:36,429 --> 00:11:40,165
and hurls its companion
across the solar system.
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00:11:41,100 --> 00:11:42,701
Triton is left alone
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00:11:42,735 --> 00:11:44,869
orbiting Neptune the wrong way.
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00:11:48,374 --> 00:11:50,842
This companion was kind of
a sacrificial lamb
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00:11:50,876 --> 00:11:53,078
that got kicked out
into the depths of space
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00:11:53,112 --> 00:11:56,381
in order for Triton itself to be
captured into Neptune's orbit.
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00:12:01,787 --> 00:12:03,088
[narrator]
Triton's strange orbit
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00:12:03,122 --> 00:12:06,124
is just one of this
weird moon's mysteries.
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00:12:09,261 --> 00:12:10,495
Voyager 2
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00:12:10,529 --> 00:12:13,932
photographs Triton up-close
in 1989.
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00:12:17,303 --> 00:12:20,305
The camera on board
captures something weird
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00:12:20,339 --> 00:12:22,974
on the surface
of this strange world.
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00:12:25,077 --> 00:12:26,911
Hidden in this grainy photograph
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00:12:26,979 --> 00:12:28,613
is a mysterious plume
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00:12:28,647 --> 00:12:30,782
that rises from
the surface of Triton.
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The plume is a geyser
of frozen nitrogen
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00:12:35,421 --> 00:12:36,955
five miles high.
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Winds in the moon's
thin upper atmosphere
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blow the vapor into trails
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00:12:44,029 --> 00:12:46,464
that are hundreds of miles long.
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When Voyager flew past Triton,
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it saw the unexpected.
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00:12:49,869 --> 00:12:52,504
There were jets of gas shooting
out from the moon's surface.
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No one expected that.
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00:12:54,340 --> 00:12:56,875
It's out at the far reaches
of the solar system.
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We expected to find
a cold, dead moon.
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00:13:00,212 --> 00:13:02,647
What the heck is going on?
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00:13:02,681 --> 00:13:06,551
[narrator] Why do geysers
blast from the surface of Triton?
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00:13:06,585 --> 00:13:09,287
And what is the power source
that drives them?
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00:13:12,491 --> 00:13:14,492
In 2019,
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00:13:14,527 --> 00:13:17,896
investigators used the
Gemini South telescope in Chile
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00:13:17,930 --> 00:13:20,098
to study Triton's icy crust.
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00:13:23,302 --> 00:13:24,803
Researchers discovered that
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00:13:24,837 --> 00:13:26,771
the ice on the surface of Triton
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00:13:26,806 --> 00:13:28,673
is a special cocktail
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00:13:28,707 --> 00:13:31,576
of carbon monoxide
and frozen nitrogen.
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00:13:31,610 --> 00:13:33,278
[Thaller] In some ways
you can think of Triton
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00:13:33,312 --> 00:13:34,979
as having a frozen atmosphere.
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00:13:35,014 --> 00:13:37,148
Our atmosphere on Earth
is mostly nitrogen
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00:13:37,183 --> 00:13:38,750
and that's true on Triton too.
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00:13:38,784 --> 00:13:41,252
But the nitrogen's frozen
into a layer of ice.
253
00:13:42,555 --> 00:13:45,256
That ice is actually
transparent to light.
254
00:13:45,291 --> 00:13:47,992
So, sunlight can get through
that transparent ice
255
00:13:48,027 --> 00:13:49,627
and heat up
little pockets in it.
256
00:13:51,797 --> 00:13:53,097
[narrator] Some types of ice
257
00:13:53,132 --> 00:13:55,900
transform directly
from a solid into gas,
258
00:13:55,935 --> 00:13:58,036
when they heat up
inside an atmosphere
259
00:13:58,070 --> 00:13:59,571
that is super thin.
260
00:14:01,740 --> 00:14:05,210
Astronomers believe that
this volatility of Triton's ice
261
00:14:05,244 --> 00:14:08,046
unlocks they mystery
of its mega geysers.
262
00:14:11,851 --> 00:14:13,685
At a point in Neptune's year,
263
00:14:13,719 --> 00:14:16,621
Triton's north pole
leans towards the Sun.
264
00:14:18,824 --> 00:14:20,892
This gives one hemisphere
of the moon
265
00:14:20,926 --> 00:14:23,928
a summer that lasts
41 Earth years.
266
00:14:25,531 --> 00:14:27,465
The rays from the Sun are weak
267
00:14:28,667 --> 00:14:31,636
but they can pass through
Triton's nitrogen ice.
268
00:14:34,106 --> 00:14:36,274
Here, they hit
a dark layer of dust
269
00:14:37,543 --> 00:14:39,644
which heats up
by just a few degrees.
270
00:14:40,613 --> 00:14:43,348
Enough to turn the ice above
into gas.
271
00:14:43,382 --> 00:14:45,416
[ice cracks]
272
00:14:45,451 --> 00:14:48,519
The pressure rises
as the gas builds up,
273
00:14:48,554 --> 00:14:51,823
until it erupts as
powerful geysers of nitrogen.
274
00:14:55,628 --> 00:14:58,997
[faint beeping]
275
00:14:59,031 --> 00:15:03,301
Voyager 2 shows that ice
giants contain many secrets.
276
00:15:05,170 --> 00:15:07,472
The data it beams back to Earth
277
00:15:07,506 --> 00:15:10,541
reveals another mystery
for astronomers to solve.
278
00:15:11,777 --> 00:15:14,312
The magnetometer
on board the probe
279
00:15:14,346 --> 00:15:16,547
detects that
the magnetic field of Uranus
280
00:15:16,582 --> 00:15:17,982
is super strange.
281
00:15:19,785 --> 00:15:23,254
The field lines
continually twist and shift.
282
00:15:23,289 --> 00:15:25,189
The magnetic poles are offset
283
00:15:25,224 --> 00:15:27,258
from the planet's
axis of rotation
284
00:15:27,293 --> 00:15:29,093
by a massive 60 degrees.
285
00:15:30,896 --> 00:15:32,897
Voyager 2 discovers later
286
00:15:32,932 --> 00:15:34,999
that the magnetic field
of Neptune
287
00:15:35,034 --> 00:15:38,102
is also irregular
and misaligned.
288
00:15:38,137 --> 00:15:40,571
When you think about
the magnetic of a planet,
289
00:15:40,606 --> 00:15:43,441
sometimes you get something
very simple, like the Earth.
290
00:15:43,475 --> 00:15:45,176
It's almost as if
there's a giant bar magnet
291
00:15:45,210 --> 00:15:46,945
going right through
the core of our planet
292
00:15:46,979 --> 00:15:49,213
with a very clear
north pole and south pole.
293
00:15:49,748 --> 00:15:50,748
With the ice giant,
294
00:15:50,783 --> 00:15:53,184
something altogether different
is going on.
295
00:15:53,218 --> 00:15:55,153
The magnetic fields are chaotic.
296
00:15:55,187 --> 00:15:57,622
The magnetic field lines
twist and turn
297
00:15:57,656 --> 00:15:59,657
like a bag of writing snakes.
298
00:15:59,692 --> 00:16:01,859
And the south pole of the planet
299
00:16:01,894 --> 00:16:04,562
is actually along the equator.
300
00:16:04,596 --> 00:16:08,166
[narrator] Why are the magnetic
fields of the ice giants twisted?
301
00:16:10,135 --> 00:16:12,904
Can a strange material
deep inside Uranus
302
00:16:12,938 --> 00:16:14,439
unlock the mystery?
303
00:16:25,818 --> 00:16:28,686
[narrator] Uranus and Neptune
304
00:16:28,721 --> 00:16:31,823
lie at the farthest reaches
of our solar system.
305
00:16:33,192 --> 00:16:35,860
Voyager 2 remains
the only mission
306
00:16:35,894 --> 00:16:38,363
to visit these
ice giant planets.
307
00:16:39,898 --> 00:16:43,234
The spacecraft discovers
that they have strange moons
308
00:16:45,104 --> 00:16:47,939
and bizarre,
twisted magnetic fields.
309
00:16:49,307 --> 00:16:53,511
Why are the magnetic fields of
Uranus and Neptune so chaotic?
310
00:16:58,650 --> 00:17:00,785
Scientists believe
the answer lies
311
00:17:00,819 --> 00:17:03,654
in discovering what
inside the ice giants
312
00:17:03,689 --> 00:17:05,656
generates their magnetic fields?
313
00:17:08,961 --> 00:17:11,696
A mass of molten iron and nickel
314
00:17:11,730 --> 00:17:14,732
sits at the center
of a rocky planet like Earth.
315
00:17:15,734 --> 00:17:17,568
This super dense liquid metal
316
00:17:17,603 --> 00:17:19,771
forms a thick and compact shell
317
00:17:19,805 --> 00:17:21,472
wrapped around
the planet's core.
318
00:17:23,509 --> 00:17:26,711
Heat drives powerful currents
inside this concentration
319
00:17:26,745 --> 00:17:28,212
of molten material.
320
00:17:29,348 --> 00:17:32,016
These deep currents
generate a magnetic field.
321
00:17:33,552 --> 00:17:36,687
The rotation of Earth
twists the currents
322
00:17:36,722 --> 00:17:40,058
into orderly streams that
move in the same direction
323
00:17:40,092 --> 00:17:41,793
as Earth turns.
324
00:17:43,228 --> 00:17:46,898
The result is that the axis
of Earth's magnetic field
325
00:17:46,932 --> 00:17:50,902
almost matches the axis
of the planet's rotation.
326
00:17:50,936 --> 00:17:52,870
Well, the magnetic field
is generated
327
00:17:52,905 --> 00:17:55,673
by rotating liquids
inside the planet
328
00:17:55,707 --> 00:17:57,308
and those liquids
are going to rotate
329
00:17:57,342 --> 00:17:58,910
along with the planet itself.
330
00:17:58,944 --> 00:18:00,378
So, it makes sense that
331
00:18:00,412 --> 00:18:02,847
the planet's geographic
north and south pole
332
00:18:02,881 --> 00:18:07,151
align with the magnetic
north and south pole.
333
00:18:07,186 --> 00:18:10,822
However, with Uranus,
we don't see that.
334
00:18:10,856 --> 00:18:13,624
[narrator] An ice giant
contains no moving metal
335
00:18:13,659 --> 00:18:15,960
at its core.
336
00:18:15,994 --> 00:18:18,463
Scientists believe
the cores of these planets
337
00:18:18,497 --> 00:18:20,031
are made from a mixture of
338
00:18:20,065 --> 00:18:23,868
rock, water,
methane and ammonia.
339
00:18:23,902 --> 00:18:26,737
So, what happens at
the center of ice giants?
340
00:18:28,140 --> 00:18:31,709
Scientists at the University
of Rochester in New York
341
00:18:31,743 --> 00:18:34,612
believe that the huge pressure
at the core of ice giants
342
00:18:34,646 --> 00:18:36,347
helps unlock the mystery.
343
00:18:36,381 --> 00:18:37,548
[beeping]
344
00:18:38,650 --> 00:18:40,118
In 2018,
345
00:18:40,152 --> 00:18:42,820
they test how this pressure
transforms water
346
00:18:42,855 --> 00:18:46,190
into weird states of matter
with strange properties.
347
00:18:51,330 --> 00:18:54,098
They use an anvil
made of diamonds
348
00:18:54,133 --> 00:18:55,833
to compress a sample of water
349
00:18:55,868 --> 00:18:59,270
to a pressure similar to that
at the core of an ice giant.
350
00:19:03,475 --> 00:19:06,844
The crust water transforms
at the molecular level
351
00:19:06,879 --> 00:19:10,548
and turns into a super-hot
jet black material
352
00:19:10,582 --> 00:19:12,416
called superionic ice.
353
00:19:15,687 --> 00:19:18,422
Its oxygen atoms
form a rigid lattice
354
00:19:18,457 --> 00:19:20,925
that hydrogen atoms
can float through,
355
00:19:20,959 --> 00:19:23,928
meaning that it can become
electrically charged.
356
00:19:26,865 --> 00:19:29,867
But this weird ice is rigid.
357
00:19:29,902 --> 00:19:32,503
So if it is at the core
of the ice giants
358
00:19:32,538 --> 00:19:34,705
it creates
a fundamental problem.
359
00:19:38,777 --> 00:19:41,179
Only moving material
inside a planet
360
00:19:41,213 --> 00:19:44,682
can act like a dynamo
and generate a magnetic field.
361
00:19:46,952 --> 00:19:48,452
The Rochester experiment
362
00:19:48,487 --> 00:19:51,489
shows that an ice giant's core
could be static.
363
00:19:52,824 --> 00:19:55,493
This means that
the planet's magnetic field
364
00:19:55,527 --> 00:19:57,128
can't come from there.
365
00:19:57,162 --> 00:19:59,630
Water ice
under the right conditions
366
00:19:59,665 --> 00:20:01,632
very compressed
to the core of a planet
367
00:20:01,667 --> 00:20:03,935
is actually stopping
the magnetic field
368
00:20:03,969 --> 00:20:06,304
going through the very center
of the planet.
369
00:20:07,506 --> 00:20:09,040
So there's gonna be
no magnetic field
370
00:20:09,074 --> 00:20:10,508
based in the core of Uranus.
371
00:20:12,077 --> 00:20:13,477
[narrator]
If the super pressurized
372
00:20:13,512 --> 00:20:15,146
ice core of an ice giant
373
00:20:15,180 --> 00:20:17,515
doesn't generate
the planet's magnetic field,
374
00:20:18,550 --> 00:20:20,051
then what does?
375
00:20:25,557 --> 00:20:28,593
One theory is that a liquid
ocean of compressed water
376
00:20:28,627 --> 00:20:30,294
exists in a thin shell
377
00:20:30,329 --> 00:20:32,863
around the solid core
of an ice giant.
378
00:20:34,266 --> 00:20:35,766
[Thaller] Farther up
from the core,
379
00:20:35,801 --> 00:20:37,702
there's this sort of
a Goldilocks Zone.
380
00:20:37,736 --> 00:20:40,304
Not too compressed,
the water can flow around
381
00:20:40,339 --> 00:20:41,939
yet still be
electrically charged,
382
00:20:41,974 --> 00:20:43,641
and there's your magnetic field.
383
00:20:45,110 --> 00:20:47,478
[narrator] How this layer
of pressurized liquid
384
00:20:47,512 --> 00:20:51,048
moves around this solid
superionic ice core,
385
00:20:51,083 --> 00:20:53,117
could unlock why
the magnetic fields
386
00:20:53,151 --> 00:20:54,952
of ice giants are chaotic.
387
00:20:58,056 --> 00:20:59,557
Deep inside Uranus...
388
00:20:59,591 --> 00:21:01,292
[rumbling]
389
00:21:01,326 --> 00:21:05,062
...lies a compressed
superionic ice core
390
00:21:05,097 --> 00:21:08,132
that is a scorching
9,000 degrees Fahrenheit.
391
00:21:10,302 --> 00:21:12,603
Somewhere in between
this rigid ball
392
00:21:12,638 --> 00:21:14,338
and the surface of the planet
393
00:21:14,373 --> 00:21:18,075
is a shell of highly
pressurized water that can flow.
394
00:21:20,812 --> 00:21:23,614
But the disconnected currents
inside this layer
395
00:21:24,983 --> 00:21:27,518
do not generate
a magnetic field that matches
396
00:21:27,552 --> 00:21:29,787
the direction
of the planet's rotation.
397
00:21:33,625 --> 00:21:36,627
So that's how the magnetic
fields of the ice giants
398
00:21:36,662 --> 00:21:39,430
can slip and become misaligned.
399
00:21:45,504 --> 00:21:48,372
Weird water unlocks
why the ice giants
400
00:21:48,407 --> 00:21:50,508
have super strange
magnetic fields.
401
00:21:52,110 --> 00:21:54,679
But these mega planets
contain more mysteries
402
00:21:54,713 --> 00:21:56,647
for astronomers to solve.
403
00:21:56,682 --> 00:21:58,149
[beeping]
404
00:21:58,183 --> 00:22:03,020
Voyager 2 sees up close, arguably,
the single strangest characteristic
405
00:22:03,055 --> 00:22:05,122
of either of these
distant planets.
406
00:22:06,692 --> 00:22:08,693
[Plait] There's a lot of
weird stuff about Uranus
407
00:22:08,760 --> 00:22:14,799
but maybe the weirdest is
that it orbits the Sun on its side.
408
00:22:14,833 --> 00:22:17,968
[narrator] Uranus leans over
98 degrees from the vertical.
409
00:22:19,371 --> 00:22:21,839
It is the only planet
in the solar system
410
00:22:21,873 --> 00:22:23,341
that is orientated this way.
411
00:22:25,344 --> 00:22:28,145
Why does this ice giant
roll around the Sun
412
00:22:28,180 --> 00:22:29,780
like a huge beach ball?
413
00:22:34,986 --> 00:22:37,154
Astronomers think
that planets form
414
00:22:37,189 --> 00:22:38,956
from a disc of gas and dust...
415
00:22:40,492 --> 00:22:43,594
orbiting a young star.
416
00:22:43,628 --> 00:22:47,598
These young worlds inherit both
their direction and axes of spin
417
00:22:47,632 --> 00:22:49,033
from the angle of the disc.
418
00:22:53,305 --> 00:22:55,272
This means that
all of the planets
419
00:22:55,307 --> 00:22:57,074
should be born with a spin axis
420
00:22:57,109 --> 00:22:59,477
that is roughly
90 degrees to the disc.
421
00:23:01,380 --> 00:23:05,249
This model predicts that
Uranus starts life upright,
422
00:23:05,283 --> 00:23:09,353
just like all the other
planets in the solar system.
423
00:23:09,388 --> 00:23:12,790
So what tips Uranus
onto its side after it forms?
424
00:23:17,829 --> 00:23:22,266
Scientists believe that a clue lies
in our solar system's violent past.
425
00:23:22,768 --> 00:23:24,635
[loud crashing]
426
00:23:25,570 --> 00:23:27,204
The early days
of the solar system
427
00:23:27,239 --> 00:23:29,540
were a chaotic maelstrom
of smash-and-grabs.
428
00:23:31,576 --> 00:23:34,512
We see evidence of this, of
course, in the form of craters
429
00:23:34,546 --> 00:23:36,380
on many bodies
in the solar system.
430
00:23:38,383 --> 00:23:42,052
[narrator] Does an ancient
mega-collision knock Uranus onto its side?
431
00:23:44,189 --> 00:23:48,192
And what are the mysterious
spots in the atmosphere of Neptune?
432
00:23:59,538 --> 00:24:04,208
[narrator] Uranus leans over so
much that it orbits the Sun on its side.
433
00:24:05,844 --> 00:24:08,946
One explanation is that
Uranus is involved
434
00:24:08,980 --> 00:24:12,082
in a mega-collision
billions of years ago.
435
00:24:13,618 --> 00:24:16,120
But what kind of cosmic crash
436
00:24:16,154 --> 00:24:18,422
can knock over an entire planet?
437
00:24:22,294 --> 00:24:26,130
Researchers at the University
of Durham in the United Kingdom
438
00:24:26,164 --> 00:24:29,733
simulate impacts between
Uranus and large protoplanets.
439
00:24:30,836 --> 00:24:33,337
They build a virtual Uranus
440
00:24:33,371 --> 00:24:37,174
and fire space objects at it
from different angles.
441
00:24:39,478 --> 00:24:42,079
These simulations show
that a head-on collision
442
00:24:42,113 --> 00:24:43,747
blows apart the virtual Uranus.
443
00:24:45,917 --> 00:24:49,620
But a sideswipe generates
just the right amount of force
444
00:24:49,654 --> 00:24:52,189
to leave Uranus spinning
on its side
445
00:24:52,224 --> 00:24:54,358
without destroying
the ice giant.
446
00:24:57,996 --> 00:25:00,397
Around four billion years ago,
447
00:25:00,432 --> 00:25:02,967
icy protoplanets
surround a young Uranus.
448
00:25:04,569 --> 00:25:09,173
One ice ball planet, twice the
size of Earth, wanders too close.
449
00:25:11,109 --> 00:25:13,177
The ice giant's immense gravity
450
00:25:13,211 --> 00:25:15,346
locks the planet
into a collision course.
451
00:25:17,249 --> 00:25:19,250
The impact knocks
Uranus backwards
452
00:25:20,652 --> 00:25:23,454
The smaller planet
disintegrates in a shower
453
00:25:23,488 --> 00:25:25,189
of water and methane ice.
454
00:25:26,291 --> 00:25:29,093
The crash leaves Uranus
tilted over permanently.
455
00:25:30,462 --> 00:25:33,430
The icy debris comes together
over time
456
00:25:33,465 --> 00:25:36,300
to form the ice giant's
27 moons,
457
00:25:36,334 --> 00:25:41,105
and a spectacular ring system,
similar to the one around Saturn.
458
00:25:41,139 --> 00:25:43,674
When you think about this
violent destructive collision
459
00:25:43,708 --> 00:25:45,709
that tilted the whole world
on its side,
460
00:25:45,744 --> 00:25:48,579
there was also a creative
flipside to it, as well.
461
00:25:48,613 --> 00:25:51,382
It generated a whole new
system of moons and rings.
462
00:25:55,220 --> 00:25:57,121
[beeping]
463
00:25:57,155 --> 00:26:00,724
[narrator] Voyager 2 arrives
at Neptune in 1989.
464
00:26:02,761 --> 00:26:05,596
Here it uncovers
another ice giant enigma.
465
00:26:08,567 --> 00:26:12,636
The spacecraft captures this
image of a mysterious cyclone
466
00:26:12,671 --> 00:26:14,471
in Neptune's
southern hemisphere.
467
00:26:17,375 --> 00:26:21,145
It is almost 8,000 miles wide.
468
00:26:21,179 --> 00:26:23,180
[Thaller] There was a
beautiful surprise waiting for us
469
00:26:23,214 --> 00:26:25,449
when Voyager finally
got out to Neptune.
470
00:26:25,483 --> 00:26:28,953
There was a giant storm
churning away in the atmosphere.
471
00:26:28,987 --> 00:26:30,654
This storm was about
the size of the Earth
472
00:26:30,689 --> 00:26:32,189
and we called it the Dark Spot.
473
00:26:33,658 --> 00:26:36,226
[narrator] The instruments
on board Voyager 2
474
00:26:36,261 --> 00:26:39,029
measured the wind speed
inside this mega-storm
475
00:26:39,064 --> 00:26:42,499
to be in excess
of 1,500 miles per hour.
476
00:26:43,735 --> 00:26:45,803
The winds are moving so fast,
477
00:26:45,837 --> 00:26:48,339
they're moving twice the speed
of a commercial airliner.
478
00:26:49,908 --> 00:26:52,176
[Plait] When you look at
pictures of Uranus and Neptune,
479
00:26:52,210 --> 00:26:55,579
they're just kinda green
and just kinda blue.
480
00:26:55,614 --> 00:26:59,149
But, in fact, these atmospheres
are incredibly dynamic
481
00:26:59,184 --> 00:27:02,086
with enormous storms
erupting all the time.
482
00:27:03,888 --> 00:27:07,057
[Thaller] The very workings of
Neptune's atmosphere are very mysterious.
483
00:27:07,092 --> 00:27:10,194
How do you form
a huge Earth-size storm
484
00:27:10,228 --> 00:27:13,197
and winds that blow that fast
at that cold temperature?
485
00:27:14,966 --> 00:27:18,335
[narrator] The Sun powers
the weather on Earth.
486
00:27:18,370 --> 00:27:21,105
Its radiation heats
the surface of our planet.
487
00:27:22,774 --> 00:27:25,275
This heat creates currents
in the atmosphere
488
00:27:25,310 --> 00:27:27,211
that move to make wind.
489
00:27:30,315 --> 00:27:33,984
Neptune is almost three
billion miles away from the Sun.
490
00:27:35,487 --> 00:27:38,222
The energy that Neptune
receives from this star
491
00:27:38,256 --> 00:27:43,027
is too weak to drive its weather
in the same way as on Earth.
492
00:27:43,061 --> 00:27:46,664
So where does the massive energy
that drives these storms come from?
493
00:27:52,270 --> 00:27:55,005
The Hubble Space Telescope
finds a clue
494
00:27:55,040 --> 00:27:57,675
almost 30 years after Voyager 2
495
00:27:57,709 --> 00:27:59,743
discovers the Great Dark Spot.
496
00:28:01,646 --> 00:28:03,147
In 2018,
497
00:28:03,181 --> 00:28:06,884
the telescope captures
this image of a new dark spot.
498
00:28:08,920 --> 00:28:11,455
This one is in the
planet's northern hemisphere.
499
00:28:13,458 --> 00:28:14,892
[Thaller] The amazing
thing about Neptune
500
00:28:14,926 --> 00:28:16,727
is how dynamic it is.
501
00:28:16,761 --> 00:28:20,030
We see evidence
of new dark spots forming.
502
00:28:20,065 --> 00:28:22,066
So this world
is very much alive.
503
00:28:22,100 --> 00:28:24,268
It may be cold,
but it's not dead.
504
00:28:27,172 --> 00:28:31,141
[narrator] Astronomers scour other
images of Neptune taken by Hubble
505
00:28:31,176 --> 00:28:34,411
for clues that can unlock
the genesis of this new spot.
506
00:28:37,449 --> 00:28:42,519
Hubble photographs the surface
of the ice giants every year.
507
00:28:42,554 --> 00:28:48,659
It creates these rolled out two-dimensional
images of the surface of Neptune.
508
00:28:48,693 --> 00:28:52,896
Astronomers use these images to
monitor changes in Neptune's atmosphere.
509
00:28:55,667 --> 00:29:00,237
They see something unusual
in this photograph from 2017.
510
00:29:01,472 --> 00:29:04,074
Mysterious clouds of methane
cover the area
511
00:29:04,109 --> 00:29:07,244
where Hubble sees
the dark spot a year later.
512
00:29:09,280 --> 00:29:13,851
[Plait] On Earth, storms form when
warm air rises carrying water vapor with it
513
00:29:13,885 --> 00:29:15,853
and that forms bright clouds.
514
00:29:15,887 --> 00:29:18,856
Well, we think a similar thing
is happening on Neptune.
515
00:29:18,890 --> 00:29:21,058
Methane is coming up
through the atmosphere,
516
00:29:21,092 --> 00:29:25,162
rises up and cools and forms these
bright white clouds we see on Neptune,
517
00:29:25,196 --> 00:29:28,832
right before the
big storm erupts.
518
00:29:28,867 --> 00:29:31,702
[narrator] These clouds are
evidence that it is an energy source
519
00:29:31,736 --> 00:29:35,405
inside Neptune that
drives the dark spot storms.
520
00:29:39,377 --> 00:29:42,146
What is this mysterious
source of energy?
521
00:29:43,948 --> 00:29:47,885
And how does it generate the
fastest winds in the solar system?
522
00:29:59,030 --> 00:30:00,998
[narrator] The storm winds
on Neptune
523
00:30:01,032 --> 00:30:03,667
exceed 1500 miles per hour.
524
00:30:05,470 --> 00:30:08,238
But how can a giant planet
made of ice,
525
00:30:08,273 --> 00:30:10,440
far away from the Sun,
526
00:30:10,475 --> 00:30:13,377
have the energy to drive these
mega-hurricanes?
527
00:30:19,818 --> 00:30:24,354
The very large telescope in Chile
takes infrared images of Neptune
528
00:30:24,389 --> 00:30:25,989
to reveal its temperature.
529
00:30:27,492 --> 00:30:31,228
This heat map shows that the
upper atmosphere of Neptune
530
00:30:31,262 --> 00:30:34,264
is -330 degrees Fahrenheit.
531
00:30:35,967 --> 00:30:38,936
But this frozen ice world
has a core temperature
532
00:30:38,970 --> 00:30:42,639
of 12600 degrees Fahrenheit.
533
00:30:42,674 --> 00:30:45,242
That is hotter than
the surface of the Sun.
534
00:30:47,145 --> 00:30:51,415
Neptune's high core temperature
is the result of the planet's formation
535
00:30:51,449 --> 00:30:52,883
billions of years ago.
536
00:30:54,485 --> 00:30:59,189
The early solar system is a massive
fast-moving disc of gas and dust.
537
00:31:00,825 --> 00:31:04,127
Gravity collapses clouds
of this gas into protoplanets.
538
00:31:05,897 --> 00:31:08,031
The temperature inside a planet
539
00:31:08,066 --> 00:31:11,134
rises as more material
compresses to grow its mass.
540
00:31:13,471 --> 00:31:18,609
[Tremblay] Neptune formed from the collapse
of gas and dust under its own gravity.
541
00:31:18,643 --> 00:31:22,579
And that collapse can lock in
a lot of that internal energy
542
00:31:22,614 --> 00:31:25,749
left over from the early days
of the solar system
543
00:31:25,783 --> 00:31:28,719
that can last within the
planet for billions of years.
544
00:31:30,355 --> 00:31:32,789
[narrator] Astronomers think
that this difference in temperature
545
00:31:32,824 --> 00:31:36,193
between Neptune's hot core
and cold atmosphere
546
00:31:36,227 --> 00:31:38,829
is what triggers the
planet's superstorms.
547
00:31:44,269 --> 00:31:48,105
The extreme heat that radiates
from Neptune's core
548
00:31:48,139 --> 00:31:51,742
vaporizes the frozen gas
close to the planet's surface.
549
00:31:55,914 --> 00:31:57,881
This forces methane gas
550
00:31:57,916 --> 00:32:00,717
high into the coldest parts
of the atmosphere,
551
00:32:00,752 --> 00:32:03,787
where it crystalizes
into wispy clouds.
552
00:32:08,493 --> 00:32:12,396
The hot rising gas beneath
finally erupts.
553
00:32:12,430 --> 00:32:14,865
It punches a hole
in the upper atmosphere
554
00:32:14,899 --> 00:32:17,301
that appears as
a Giant Dark Spot.
555
00:32:19,404 --> 00:32:22,506
The extreme temperature
difference between the gases
556
00:32:22,540 --> 00:32:24,908
generates mega
convection currents
557
00:32:24,943 --> 00:32:28,178
that whip the spot into
a supersonic vortex.
558
00:32:31,215 --> 00:32:35,152
The driving force behind
Neptune's mysterious mega winds
559
00:32:35,186 --> 00:32:38,121
is not the final mystery
the ice giants pose.
560
00:32:39,791 --> 00:32:43,026
Uranus is 14 times
more massive than Earth.
561
00:32:44,429 --> 00:32:48,632
Neptune is a whopping 17 times
more massive.
562
00:32:48,666 --> 00:32:53,203
These huge worlds prowl the
farthest reaches of the solar system
563
00:32:53,237 --> 00:32:58,208
between 1.8 and 3 billion
miles from the Sun.
564
00:32:58,242 --> 00:33:02,379
This strange combination of
supersize and distant position
565
00:33:02,413 --> 00:33:06,016
presents a big puzzle
for astronomers to solve.
566
00:33:06,050 --> 00:33:08,051
[Oluseyi] One of the mysteries
of Uranus and Neptune
567
00:33:08,086 --> 00:33:10,454
is their location
in the solar system.
568
00:33:10,488 --> 00:33:12,389
They're so far away from the Sun
569
00:33:12,423 --> 00:33:14,891
that there would not
have been enough material
570
00:33:14,926 --> 00:33:19,296
in the early solar system to
build large planets of that size.
571
00:33:19,330 --> 00:33:22,666
It shouldn't be possible for
these guys to exist where they do.
572
00:33:22,700 --> 00:33:23,934
But they do.
573
00:33:29,440 --> 00:33:34,878
[narrator] The early solar system
is a swirling disc of gas and dust.
574
00:33:34,912 --> 00:33:38,548
When the Sun ignites, its heat
blows away the lighter elements.
575
00:33:40,618 --> 00:33:43,086
Over 400 million miles out,
576
00:33:43,121 --> 00:33:47,524
it is cold enough for these
elements to condense as gas and ice,
577
00:33:47,558 --> 00:33:49,893
and settle in a band
around the Sun.
578
00:33:53,264 --> 00:33:59,036
This material binds together to form
the beginnings of Jupiter and Saturn.
579
00:33:59,070 --> 00:34:03,340
These planets grow larger as they
absorb more and more gas and dust.
580
00:34:05,977 --> 00:34:08,412
But where Neptune
and Uranus orbit,
581
00:34:08,446 --> 00:34:11,148
the raw materials to build
giant planets
582
00:34:11,182 --> 00:34:13,316
are in much shorter supply.
583
00:34:16,287 --> 00:34:20,023
So how is it possible for the
ice giants to form this far out?
584
00:34:23,694 --> 00:34:26,029
[Tremblay] To build a planet,
especially a giant one,
585
00:34:26,064 --> 00:34:29,166
we need countless tiny
rocky and icy bodies
586
00:34:29,200 --> 00:34:32,102
to come together,
to grow over time.
587
00:34:32,136 --> 00:34:34,738
And we think that where we see
these planets nowadays,
588
00:34:34,772 --> 00:34:36,807
in the far outskirts
of our solar system,
589
00:34:36,841 --> 00:34:38,909
this material was
just too scarce
590
00:34:38,943 --> 00:34:40,577
to grow planets that large.
591
00:34:42,313 --> 00:34:45,126
[narrator] Astronomers arrive
at an astonishing conclusion
592
00:34:45,150 --> 00:34:46,716
to explain this anomaly.
593
00:34:48,219 --> 00:34:51,721
The ice giants come from
somewhere else in the solar system.
594
00:34:53,324 --> 00:34:54,958
[Plait] One possible
solution is that
595
00:34:54,992 --> 00:34:58,228
Uranus and Neptune didn't form
where they are now.
596
00:34:58,262 --> 00:35:00,297
If they formed
closer into the Sun,
597
00:35:00,331 --> 00:35:02,099
there would have been
enough material
598
00:35:02,133 --> 00:35:03,934
to create such large planets.
599
00:35:03,968 --> 00:35:08,839
And then somehow, Uranus and
Neptune moved out to where they are today.
600
00:35:08,873 --> 00:35:11,041
[narrator] Why did these
ice giants migrate
601
00:35:11,075 --> 00:35:14,744
to the farthest reaches
of the solar system?
602
00:35:14,779 --> 00:35:19,749
And what was the role of these planets
in shaping the solar system we see today?
603
00:35:30,728 --> 00:35:33,396
Astronomers think that
Neptune and Uranus
604
00:35:33,431 --> 00:35:36,566
were not born in the far
reaches of the solar system,
605
00:35:36,601 --> 00:35:37,801
where they are today.
606
00:35:41,038 --> 00:35:43,874
Instead, they formed
closer to the Sun
607
00:35:43,908 --> 00:35:46,309
and then moved
farther and farther out.
608
00:35:49,046 --> 00:35:52,349
What triggered this epic
migration of the ice giants?
609
00:35:57,421 --> 00:36:02,859
Scientists believe the answer
is locked inside meteorites.
610
00:36:02,894 --> 00:36:06,630
Meteorites are the parts of ancient
asteroids that collide with Earth.
611
00:36:12,703 --> 00:36:16,139
They contain tiny quantities
of radioactive elements.
612
00:36:18,176 --> 00:36:21,478
These elements allow
scientists to date the meteorites,
613
00:36:21,512 --> 00:36:24,848
to discover the exact age of
the asteroids they come from.
614
00:36:25,917 --> 00:36:27,617
[Plait] Meteorites that
fall to Earth
615
00:36:27,652 --> 00:36:30,654
have elements like uranium,
which is radioactive.
616
00:36:30,688 --> 00:36:33,757
And this radioactive decay
that uranium undergoes
617
00:36:33,791 --> 00:36:35,158
is like a ticking clock
618
00:36:35,193 --> 00:36:37,294
that allows us to get
the age of the meteorite.
619
00:36:39,063 --> 00:36:41,498
[narrator] The radioactive
clock starts ticking
620
00:36:41,532 --> 00:36:46,102
when the space rock first forms
at the birth of the solar system.
621
00:36:46,137 --> 00:36:50,907
That means all meteorites should
be around 4.6 billion years old.
622
00:36:52,043 --> 00:36:54,878
But scientists make
an extraordinary discovery
623
00:36:54,912 --> 00:36:58,582
when they date the space rocks
that fall to Earth.
624
00:36:58,616 --> 00:37:01,718
One that can unlock the
mystery of why the ice giants
625
00:37:01,752 --> 00:37:04,654
moved farther out
across the solar system.
626
00:37:11,862 --> 00:37:14,931
[Plait] When we get the ages of
meteorites through radioactive decay,
627
00:37:14,966 --> 00:37:18,735
we find that most of them are about
the same age as the solar system itself.
628
00:37:18,769 --> 00:37:22,505
However, a lot of meteorites
have a significantly younger age.
629
00:37:24,075 --> 00:37:26,276
[narrator] The clocks of
these younger asteroids
630
00:37:26,310 --> 00:37:30,547
start ticking around 80 million
years after the solar system forms.
631
00:37:32,516 --> 00:37:35,986
Super-heating and melting
the minerals inside asteroids
632
00:37:36,020 --> 00:37:38,388
resets their radioactive clocks.
633
00:37:39,557 --> 00:37:41,191
Scientists believe that
634
00:37:41,225 --> 00:37:44,894
only a super-violent
solar system-wide catastrophe
635
00:37:44,929 --> 00:37:47,264
could generate
temperatures high enough
636
00:37:47,298 --> 00:37:49,065
to melt down so much rock.
637
00:37:49,800 --> 00:37:51,234
We're talking destruction
638
00:37:51,269 --> 00:37:53,370
on a truly unprecedented scale.
639
00:37:53,404 --> 00:37:56,673
Entire worlds colliding
together and getting obliterated,
640
00:37:56,707 --> 00:37:59,442
asteroids flying
every which way you look.
641
00:37:59,477 --> 00:38:02,479
If you were to actually look
up in the sky during this time,
642
00:38:02,513 --> 00:38:05,482
you'd have seen this destructive
light show unlike any other.
643
00:38:07,184 --> 00:38:08,785
[Plait] Objects were
streaming around,
644
00:38:08,819 --> 00:38:10,987
smashing into each other,
and remelting.
645
00:38:11,856 --> 00:38:13,556
And that's why these meteorites
646
00:38:13,591 --> 00:38:16,092
seem to be younger than
the solar system itself.
647
00:38:17,895 --> 00:38:19,863
[narrator] Scientists
think this disaster
648
00:38:19,897 --> 00:38:22,332
impacts all the planets
in the solar system...
649
00:38:23,067 --> 00:38:25,435
including the ice giants.
650
00:38:26,704 --> 00:38:29,472
But what triggers
this mega violent event?
651
00:38:30,508 --> 00:38:33,243
And how does it banish
Uranus and Neptune
652
00:38:33,277 --> 00:38:36,846
to a region of space billions
of miles from the Sun?
653
00:38:42,153 --> 00:38:45,221
Astronomers believed that
the proximity of the ice giants
654
00:38:45,256 --> 00:38:48,658
to their gas giant neighbors,
Jupiter and Saturn,
655
00:38:48,693 --> 00:38:51,261
unlocks the mystery.
656
00:38:51,295 --> 00:38:53,797
[Thaller] Probably all four
major worlds of our solar system,
657
00:38:53,831 --> 00:38:55,899
Jupiter, Saturn,
Uranus and Neptune
658
00:38:55,933 --> 00:38:58,168
were competing for
planet-building materials,
659
00:38:58,202 --> 00:39:00,970
jockeying for position
in a young solar system.
660
00:39:01,005 --> 00:39:03,840
All of a sudden, you're kind
of playing planetary pinball.
661
00:39:05,109 --> 00:39:07,944
[narrator] Around
4.6 billion years ago,
662
00:39:07,978 --> 00:39:11,614
Jupiter, Saturn,
Neptune and Uranus
663
00:39:11,649 --> 00:39:15,719
orbit much closer to each
other than they do today.
664
00:39:15,753 --> 00:39:19,789
Back then, their proximity
causes gravitational chaos.
665
00:39:21,392 --> 00:39:24,794
The huge gravity of
the larger Jupiter and Saturn
666
00:39:24,829 --> 00:39:27,664
forces out
the smaller ice giants.
667
00:39:27,698 --> 00:39:32,502
And they begin an epic journey
across the solar system.
668
00:39:32,536 --> 00:39:36,506
One theory is that they even
swap places along the way.
669
00:39:38,876 --> 00:39:42,145
Uranus and Neptune
travel billions of miles
670
00:39:42,179 --> 00:39:46,216
to end up in the sparse outer
reaches of the solar system.
671
00:39:49,453 --> 00:39:51,154
[Thaller] The truth
of the matter is that
672
00:39:51,188 --> 00:39:53,623
if you're jostling with Jupiter
and Saturn for real estate,
673
00:39:53,657 --> 00:39:54,724
even an ice giant
674
00:39:54,759 --> 00:39:56,226
really doesn't stand
much of a chance.
675
00:39:56,260 --> 00:39:57,727
It's out to the suburbs.
676
00:39:58,996 --> 00:40:00,397
[narrator] This
gravitational battle
677
00:40:00,431 --> 00:40:03,500
between Jupiter, Saturn
and the ice giants
678
00:40:03,534 --> 00:40:07,337
triggers an intense asteroid
bombardment on the solar system.
679
00:40:09,306 --> 00:40:13,320
Space rocks smash together
in mega impacts
680
00:40:13,344 --> 00:40:16,913
in the most violent period
of the solar system's history.
681
00:40:18,149 --> 00:40:21,418
This stress melts and reforms
the asteroids,
682
00:40:21,485 --> 00:40:24,521
and resets their
radioactive clocks.
683
00:40:24,555 --> 00:40:26,790
Over time, many of these rocks
684
00:40:26,824 --> 00:40:29,225
drift into
the inner solar system
685
00:40:29,260 --> 00:40:31,895
and crashed to Earth
as meteorites.
686
00:40:37,468 --> 00:40:39,836
The migration of
Uranus and Neptune
687
00:40:39,870 --> 00:40:44,707
explains why the ice giants
orbit so far from the Sun.
688
00:40:44,742 --> 00:40:48,077
Their movement reshuffles
the entire solar system.
689
00:40:48,112 --> 00:40:51,381
And locks it into the
configuration we know today.
690
00:40:57,621 --> 00:41:00,890
The ice giants are the weirdest
worlds in the solar system.
691
00:41:02,159 --> 00:41:05,028
From Neptune's
superfast winds...
692
00:41:05,062 --> 00:41:08,698
and the giant geysers
on its moon, Triton...
693
00:41:08,732 --> 00:41:12,168
to the bizarre sideways
rotation of Uranus...
694
00:41:12,203 --> 00:41:14,170
and it's strange magnetic field
695
00:41:14,205 --> 00:41:16,439
powered by
an exotic form of water...
696
00:41:17,908 --> 00:41:21,544
these two planets
break all the rules.
697
00:41:21,579 --> 00:41:24,681
Uranus and Neptune
are dynamic, interesting,
698
00:41:24,715 --> 00:41:27,617
and above all else,
weird places.
699
00:41:28,953 --> 00:41:30,587
[Thaller] The ice giants
prove to us that
700
00:41:30,621 --> 00:41:33,122
there's no such thing
as a normal planet.
701
00:41:33,157 --> 00:41:35,525
They work in
an entirely different way
702
00:41:35,559 --> 00:41:38,561
than any other type of planet
that we know of.
703
00:41:38,596 --> 00:41:40,797
[Oluseyi] They just completely
blow away our ideas
704
00:41:40,831 --> 00:41:42,765
of how planets are formed.
705
00:41:42,833 --> 00:41:45,602
So far, we only had a glimpse
of these ice giant planets.
706
00:41:45,636 --> 00:41:47,403
And the next probes
that go there,
707
00:41:47,438 --> 00:41:49,172
might find they're even weirder
708
00:41:49,206 --> 00:41:50,206
than we think now.
709
00:41:51,642 --> 00:41:52,775
[narrator] Our solar system
710
00:41:52,810 --> 00:41:54,878
would be a very different place,
711
00:41:54,912 --> 00:41:58,381
if it were not for these
strange oddball worlds.