Original subtitles

- In the cold, dark expanse of our solar system,

beyond the asteroid belt, lie the giant planets.

Some can be seen with the naked eye,

others only glimpsed once by a passing probe.

We are again sending cameras to the edge of the solar system

to bring us new insights into the evolution of our worlds.

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Pioneer 10 and 11 made the first passage

through the asteroid belt,

leading the way for the venerable Voyager missions.

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These two probes made a grand tour

of the outer solar system,

before slipping away into interstellar space.

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Jupiter, the first and greatest of the outer planets

with its broiling sky, has had fleeting visits

from other missions, like Ulysses, Galileo, and Cassini,

each adding to the mosaic of Jupiter,

and its violent atmosphere.

- My name is Amy Simon-Miller,

and I study the atmospheres of the Jovian planets.

Weather on Jupiter is confined to a rather thin layer

kind of high up in the atmosphere,

so the tops of the clouds are what we're seeing

when we look at Jupiter.

One thing we're seeing in the southern part

of the equatorial region,

is little V-shaped clouds or chevrons,

and we wanted to understand

how those are moving in the atmosphere.

- What we think chevrons are,

are simply holes in the clouds.

There are simply areas where we don't see

any bright white clouds.

- The Cassini mission flew by Jupiter in the year 2000,

and because it was a slow, distant flyby,

we got a lot of coverage of the planet

over a long time period.

So we were able to put those images together

and make movies.

- Using these movies, we observed Rossby waves

that caused north-south manners in a jetstream

south of the equator.

With new movies, we instead focused on hot spots.

Hot spots are unique because we believe

that there is a Rossby wave

similar to what we previously detected,

but instead of this Rossby wave moving north-south,

it primarily moves up and down in the atmosphere.

The downward portion of the wave pushes air

down into warmer layers of the atmosphere.

This causes any clouds that are embedded within the wave

to evaporate and prevents further clouds from forming.

So at any given time, there are approximately eight to 10

hot spots in Jupiter's atmosphere that are spaced

roughly evenly apart from one another.

We believe that each of the downward portions

of this Rossby wave corresponds to the hot spots

that we see on Jupiter.

This new finding is exciting because it will allow us

to re-examine the Galileo probe data

and allow us to better understand it

and better place it in the context of Jupiter's

overall global climate and atmosphere.

- The latest probe to be specifically aimed

for Jupiter is Juno.

Launched 2011, the probe will reach Jupiter

after a five-year journey.

Juno's goal is to investigate Jupiter's interior structure

and magnetosphere and help improve our understanding

of the formation of the planet

and therefore the history of our solar system.

- Juno spins like a propeller,

where the propeller's kind of facing the sun

because they're all solar powered.

If you spin something, it stays spinning,

it's like a gyroscope.

We can use the spinning spacecraft

to let each instrument get its turn to see Jupiter.

We get to go very close to the planet,

inside the radiation belts,

instead of outside the radiation belt.

We're in a polar orbit,

so by small adjustments of the timing,

we can map the entire planet.

We can get repeated stripes at different longitudes,

as Jupiter spins underneath us.

- It does mean that Juno is going to see

the polar regions to a greater extent,

than with other spacecraft,

but I think the most important thing

is that it gets in very close to the planet.

As part of that ellipse, brings it in a few thousand miles

above those cloud tops, very close near the equator.

- We're gonna go over the poles of Jupiter.

That means we can study the magnetosphere

in a different way.

- A magnetosphere is the sphere of influence

of a magnetic field.

So a planet that has a magnetic field

has a magnetosphere when its sphere of influence

extends beyond the planet, out into space,

and affects the region around it.

The magnetosphere of Jupiter is vast.

So if you think of Jupiter being 10 times

the size of the Earth, and the magnetosphere

is a hundred times the size of Jupiter.

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- The Juno probe is the furthest NASA has sent

a solar powered spacecraft.

Sunlight provides 25 times less energy than on Earth,

Which means it requires advanced solar power technology,

with solar cells which are both 50% more efficient,

and more radiation tolerant than silicon cells.

The craft also houses an electronics vault,

which is radiation shielded to protect

the electronics aboard from the intense

and deadly radiation environment around Jupiter.

The probe carries a full set of sensors.

A microwave radiometer for atmospheric sounding

and composition study.

Plasma and energetic particle detectors.

A vector magnetometer.

A radio plasma wave experiment and ultraviolet,

and an infrared imager.

Plus, a color camera called JunoCam.

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- In Roman mythology, which of course,

is rooted from Greek mythology,

Juno was the wife

and sister goddess of Jupiter,

and Jupiter was sort of being naughty with some friends,

so he cast a veil of clouds around himself and his friends,

but of course, Juno was a fairly powerful god herself

and used her powers to look right through the clouds

and see the true nature of Jupiter

and understand what he was really up to.

And that's exactly what the Juno spacecraft does for us,

is that it goes there with special instruments

in a special orbit, and uses its powers

to see right through Jupiter's clouds

and understand its true nature,

which is holding these secrets for us

about how the solar system formed

and where we all came from.

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- A longstanding feature of the storms of Jupiter

is the Great Red Spot.

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Large enough to swallow the Earth,

this storm system has been studied since the 19th century.

Then, it was measured at a little over

41,000 kilometers on its long axis.

Voyager 1 and 2 measured it at over 23,000 kilometers,

and recent observations by the Hubble Space Telescope

have the Red Spot at only 16,500 kilometers long.

It seems the rate of shrinkage is increasing.

One day it will probably vanish all together.

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Juno will also help confirm the theory that Jupiter

was the first of the planets in the solar system

to form from the primordial disc of dust and gas

some 4.6 billion years ago.

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- I would expect Juno to tell us

more about how planets work.

Meaning, how the heat gets out,

what kinds of flows exist inside the body,

how magnetic fields get generated.

Learning what Jupiter is made of,

we will learn such a wide range of things.

For indeed, Jupiter is the most massive planet

in the solar system.

It is the body you want to understand,

in order to understand the architecture

of everything else, including Earth.

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- Juno's year-long mission will end with a de-orbit burn

and a slow descent into the upper atmosphere,

where it will continue to send back

scientific data until its destruction.

Perhaps the jewel of the solar system is Saturn,

with her spectacular rings.

All four of the outer planets have rings of ice and rock,

but Saturn's is the most complicated,

and with thousands of ringlet, the most visible.

There are several groups of rings

classified A through to G.

Some are formed by shepherd moons within the rings,

and by gravitational tidal effects from others outside.

Yet some gaps are still unexplained.

The current spacecraft at Saturn is Cassini,

on its second extended mission,

the Cassini Solstice Mission,

which is expected to be completed in 2017.

It continues to watch the planet-sized storms

in the atmosphere.

- Great white spots on Saturn

are these large storms that erupt

about once every year on Saturn.

A year on Saturn is 29 Earth years.

The great white spot that erupted in December 2010

initially presented itself as a small, little white

fluffy cloud that came up.

And various instruments on Cassini were seeing it,

and ground-based instruments seeing it as well.

And as the days progressed, the storm got larger,

and then it got sheared from the top

and the bottom of the storm on either side of it,

and it wrapped all the way across the planet.

We'd never before been able to study a storm system

of this magnitude in the infrared,

so we are very fortunate at this time

to have a spacecraft in orbit

and excellent ground-based facilities

allowing us to make a historical record

of this great white spot.

And that will allow us to compare it in future generations,

when the next one happens.

- Another phenomenon is a hexagon of clouds

around the north pole of Saturn,

which has recently come into the light.

- Cassini has been in orbit around Saturn for nine years,

and we've been following this hexagon,

which surrounds the north pole.

It's bigger than two Earths,

and it's a wandering jetstream

But it's been winter in the north,

so we have not been able to see

what's at the center of the hexagon.

But now it's spring.

And what we found at the center of the hexagon

is a Saturn hurricane.

This is a view from directly over the north pole,

which is made possible by the orbit of the spacecraft,

which is now taking us over the poles.

The winds are flowing at 300 miles an hour,

which is four times hurricane force.

The fluffy white clouds in the center

are about the size of Texas.

We can use special filters to measure

the heights of the clouds.

And red are low clouds, and the green are high clouds.

We call it a Saturn hurricane because it has the eye,

it has the high winds, but it's different

from an Earth hurricane

because it's locked to the north pole.

And unlike a terrestrial hurricane,

there's no ocean underneath,

and that's one of the puzzles we're trying to figure out.

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- A phenomenon first observed on Saturn

by Pioneer 11 in 1979,

and common to Earth as well, are polar auroras.

These magnetic generated light shows

are far more spectacular on Saturn,

rising hundreds of miles above the planet's poles.

And unlike on Earth, where bright displays

fizzle after only a few hours,

auroras on Saturn can shine for days.

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Auroras are produced when speeding particles

accelerated by the sun's energy

collide with gasses in a planet's atmosphere.

The gasses fluoresce, emitting flashes of light

at different wavelengths.

The Hubble Space Telescope has been watching them closely.

- Starting in 2016, ending in 2017,

these orbits will take us up and over

the north and south poles of the planet.

- We're actually going to dive in between

the innermost edge of the D ring

and the upper atmosphere of the planet itself.

- From that, we're gonna learn

how is Saturn constructed from inside out?

- We'll also get the magnetic field of the planet,

the mass of the rings for the very first time,

and get to sample a place that no spacecraft

has ever flown before.

- This is a mission that cannot be duplicated,

so we really want to take advantage of this opportunity

to observe seasonal variation in the system.

- Uranus has had only one visitor from Earth, Voyager 2.

Like the other gas giants, Uranus has a ring system,

a magnetosphere, and numerous moons.

There, the similarities end.

Images from Voyager reveal the featureless atmosphere,

with no cloud patterns or storms.

Uranus differs in its orientation as well.

Tilted on to its side, its poles lie where other planets

have their equators.

Its magnetosphere is off-center and tilted as well,

generating an unusual asymmetrical field.

This causes Uranus's auroras to be well off the poles.

Observations from Earth have shown seasonal change,

and increased weather activity

as Uranus approached its equinox in 2007.

The wind speeds on Uranus

can reach 250 meters a second.

Although there are currently no scheduled missions

to Uranus, there have been several proposals put forward,

both jointly from ISA and NASA, and JPL,

including both nuclear and solar powered probes,

and an atmospheric descent probe.

Ion propulsion is favored because it allows a greater mass

to be sent to the planet.

Ideally, a probe could be launched in 2020,

with a 13-year cruise to Uranus.

As this is considered a low priority mission,

no funding has yet been allocated.

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The eighth and last planet in our solar system is Neptune,

the last of the gas giants.

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Made of hydrogen and helium,

it has trace amounts of methane,

which gives the planet its beautiful blue color.

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It, too, has only been visited once by Voyager.

The detailed images taken at that time

revealed white clouds, and massive storm

marring its atmosphere with supersonic winds.

- The storm revolves around the planet every 18 hours.

And then it rotates around its own axis,

like a big glob of pizza dough, every 16 days.

- Voyager also identified the ring system,

and confirmed 14 moons.

Triton is its largest, and is believed to have been captured

by the planet from the outer Kuiper belt.

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Voyager also discovered Neptune's magnetic field

was off-center and tilted, not unlike Uranus.

Both Uranus and Neptune have had very little close-up study,

and various missions have been proposed

to fill the gap in our understanding of these ice giants.

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NASA has looked into several possible missions

back to Neptune, perhaps a similar probe

designed to that Cassini Huygens.

But, due to fiscal and other constraints,

none have been approved.

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- The Voyager mission to the outer planets

has certainly been a journey of a lifetime.

Having encountered Triton as the last world we would visit,

which I don't see how any of the scientists

could have been happier.

- Next stop was Pluto.

When New Horizons was conceived, built, and launched,

Pluto was still a planet.

The downgrade to dwarf made little difference

to its investigation.

- Well, you know, the key to planetary science is,

that you really have to go places to get the resolution,

to get up close enough to really see what's going on.

We wanna get up close and personal.

- New Horizons is the first, really, of a whole new breed

of spacecraft, that is focusing on a very specific task.

- For this mission, the questions are basic.

What do Pluto and Charon look like,

and what are they made of?

- We have to really be disciplined and say,

we can't do everything.

Let's focus on the primary questions

and design the instruments

to answer those primary questions.

- New Horizons was built light

and launched on a very powerful rocket,

breaking all previous speed records

when it left Earth on a solar escape trajectory

at 16.26 kilometers per second.

The spacecraft passed the orbit of the moon

in just nine hours.

It then cruised for just one year to reach Jupiter,

where it was given a gravity boost,

increasing its speed by two kilometers per second,

and cutting the travel time to Pluto by three years.

New Horizons was the first to visit the dwarf planet,

and Charon, its largest moon.

Pluto failed one of the three criteria

to remain a fully fledged planet.

It has not cleared the neighborhood around its orbit.

Pluto is part of the Kuiper belt,

and not the only dwarf planet residing there.

This is an image of Pluto at its closest approach.

It still remains a treasure trove of scientific questions,

and hopefully answers, about the origins

and evolution of the solar system.

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From Pluto's flyby, it is on

to the unknowns of the Kuiper belt.

The most numerous objects in the solar system

of the ice dwarf planet that make up

this doughnut-shaped region on the edge of the solar system.

- it's kinda like the asteroid belt, but much bigger,

it has hundreds of times more objects in it

than the asteroid belt.

- The spacecraft will visit some

of these objects in its travels.

- Once you have the orbit,

and we know where the spacecraft is,

and where it's going to be,

we can figure out how much fuel

the spacecraft is gonna need to use

to get to these objects.

- After some careful calculations.

- It looked like we might actually have to burn the engines

to miss the object, which was pretty exciting concept.

You know, it's good thing we looked,

'cause you wouldn't want to run into one of these things.

These cold classicals,

they're pretty much as they were

4.5 billions years ago.

They're little fossils.

That's incredible. (laughs)

We have no idea what they're gonna look like.

- New Horizons will continue to explore