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Jupiter is our solar system's largest planet.
It's more than twice the mass
of all the other planets combined.
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Its swirly atmosphere moves in bands
at different latitudes,
and it's Great Red Spot is thought to be a perpetual storm.
Recently, images from a new probe
that has flown above Jupiter's poles
reveal a completely different planet.
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The ancient Romans knew Jupiter
as the celestial representation of the king of the gods.
In 1610, Galileo, using his newly improved telescope,
saw Jupiter's moons and could see they orbited the planet,
evidence that not everything revolved around the Earth,
as the church declared.
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Though better telescopes improved our view of Jupiter,
it was not until 1964 that Gary Flandro,
a graduate student working part time at NASA's JPL,
understood there was a way
to get a clearer look at Jupiter.
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By plotting the positions of the outer planets,
He realized that a rare alignment would enable a spacecraft,
launched in 1977, to visit Jupiter, Saturn,
Uranus, and Neptune.
NASA jumped to the opportunity
and began work on twin craft
for what was then known as the Planetary Grand Tour.
To limit any surprises, two basic spacecraft
known as Pioneer 10 and 11 were quickly built.
They would go ahead of the Grand Tour missions
to send back information about the environment.
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Pioneer 10 was launched toward Jupiter in March, 1972.
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It was the first spacecraft across the asteroid belt
that lay between Mars and Jupiter,
and because it was the first probe on a trajectory
that would take it out of the solar system,
it carried a plaque identifying its origin.
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By December, 1973, Pioneer 10
was sending back pictures of Jupiter
clearer than anything that had been seen before.
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Approaching Jupiter, it encountered levels of ion radiation
10,000 times more intense
than the radiation belts surrounding Earth.
As the probe skimmed past the giant planet,
it gained speed.
Leaving Earth, Pioneer 10 was moving
at 51,000 kilometers per hour.
Departing Jupiter, it had more than doubled its speed.
This gravitational slingshot effect
made the Grand Tour possible.
The Grand Tour craft recently renamed Voyager 1 and 2
were due to be transferred to Cape Canaveral
for launch integration when news
of Jupiter's extreme radiation environment came through.
The electron radiation that Jupiter
had generated false commands within Pioneer 10.
With the far more sophisticated Voyagers,
this presented problems.
Local supermarkets were stripped
of their stocks of kitchen grade aluminum foil,
which was then used to shield critical cables.
Without this last minute alteration,
electrical pressures of up to 40,000 volts
would have been induced in the Voyager's subsystems
as the craft passed Jupiter.
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Voyager 2 was launched in August, 1977.
Its trajectory meant that it could visit Jupiter, Saturn,
Uranus and Neptune.
Voyager 1 left 16 days later.
It's different, faster trajectory,
only allowed flybys of Jupiter and Saturn
and various large moons.
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At the time,
the Voyager spacecraft were the most sophisticated probes
to be launched.
Because they were to operate at huge distances from the sun,
solar panels could not be used as a power source.
They were equipped
with radioisotope thermoelectric generators
which use the heat from the decay of plutonium-238
to generate power.
As Voyager 1 approached Jupiter in January, 1979,
it began sending image sequences
that showed a complex and dynamic planet.
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The planet's giant Red Spot
was revealed as a vast rotating storm.
In 1665, Giovanni Cassini
described a permanent spot on Jupiter,
which was regularly observed into the 1700s.
It was not until the late 1800s
that Jupiter's spot was described as red.
And it's uncertain
whether the historic observations of Jupiter spot
refer to the same feature
or a phenomenon that regularly manifests
in Jupiter's atmosphere.
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Voyager 1 made its closest approach early in March, 1979.
As the probe neared Jupiter, the activity
at NASA's jet propulsion laboratory became intense.
This was the nature of the Voyager's flyby missions.
There were long quiet cruise phases between the planets
followed by brief periods
when the flow of information
from the craft overwhelmed researchers.
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One of the biggest contributions made by the Voyagers
was the transformation
in our understanding of the Galilean moons.
Previously, just dots of light,
Jupiter's four largest moons
were each distinct and completely different.
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The first surprise was the inner moon, Io.
It's a sulfurous yellow in appearance,
and one particular long duration exposure
revealed an out plume.
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Rather than being a cold dead world,
the gravitational squeezing Io receives
from its giant neighbor,
heats the moon's interior.
The plume was a volcanic eruption
ejecting material hundreds of kilometers above the surface.
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In July, 1979, three months after Voyager 1
had moved beyond Jupiter,
Voyager 2 made its closest approach.
It was able to examine different moons more closely
than its twin.
Europa was the next surprise.
It is highly reflective
and has the smoothest surface
of any body in the solar system.
Further observation revealed pressure ridges
reminiscent of polar ice flows on Earth.
Europa is a frozen world
with a vast ocean beneath a thick cross-device.
Like Io, it is heated from within by tidal flexing.
As Voyager 2 continued towards Saturn,
planetary researchers were left with large amounts
of raw data about Jupiter still to be processed.
The Voyager missions left us with a basic view
of the Jovian system,
but they had raised more questions
than they were able to answer.
It will be more than 10 years
before Jupiter received another visitor from Earth.
Ignition and liftoff
of Discovery and the Ulysses spacecraft
bound for the polar regions of the sun.
In October, 1990,
the space shuttle, Discovery
lifted the European Ulysses spacecraft to low Earth orbit.
From there, it was boosted on a mission
to observe the sun,
but first it would pass Jupiter.
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All the planets orbit the sun in the same direction
in roughly the same plane.
This is called the ecliptic
and it developed from the spinning disc of dust and gas
that formed our solar system.
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The designers of the Ulysses spacecraft
wanted to see the sun from an orbit above its poles.
Jupiter's extreme gravitation
was used to bend the probe's flight path out of the ecliptic
so it could make north-south orbits of the sun.
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Ulysses was not the only probe
to take advantage of Jupiter's gravity,
both the Cassini probe to Saturn launched in 1997
and the New Horizons probe to Pluto launched in 2006,
were able to reduce their flight times by years
with Jupiter flybys.
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These probes were able to make meaningful observations
while passing the giant planet.
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In the clean rooms of the jet propulsion laboratory,
a new probe was taking shape.
Galileo would be the first spacecraft
to go into orbit around Jupiter.
It's 4.8 meter antenna was folded like an umbrella
only to be deployed when safely on the way to Jupiter.
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Originally scheduled to launch in 1986,
it sat in storage for years
after the space shuttle, Challenger exploded.
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10, nine--
It launched aboard a space shuttle, Atlantis
in October, 1989.
Five, four, three, two, one.
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We have ignition and liftoff
of Atlantis and the Galileo spacecraft
down for Jupiter.
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New rules governing shuttle launches
meant a change in the booster
to push Galileo out of Earth orbit.
The less powerful, solid fuel upper stage now stipulated
sent Galileo toward Venus for a gravity assist.
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The new flight path meant Galileo
was traveling to a hotter part of the solar system.
It was decided to keep the heat sensitive antenna furled
until after the spacecraft looped back past Earth.
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Galileo made two close passes of Earth
each time gaining more speed.
Its first pass was in December, 1990,
more than a year after its launch.
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A further year on when it passed Earth again,
the high gain antenna was only partially open.
After months of trying different techniques
to deploy the antenna,
mission engineers concluded that long periods in storage
had caused lubricant to the tips
of the antennas' ribs to dissipate.
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Researchers would rely on Galileo's smaller antenna
with data delivered at slower rates.
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During the cruise to Jupiter,
Galileo encountered several asteroids.
This is Ida.
The first asteroid we've learnt of
with its own moon, Dactyl.
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In July, 1995,
while it was still six months away
from its closest encounter with Jupiter,
Galileo ejected a small probe
designed to enter the atmosphere
and sample its chemical composition.
The probe lasted for an hour in Jupiter's atmosphere.
The data was relayed to Galileo
and recorded for subsequent transmission back to Earth.
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It's analysis revealed hardly any water vapor,
which was unexpected
and other elements particularly helium
were detected at far lower levels than predicted.
The probe experienced areas of extreme heat and cold
suggesting heat is being released
from the planet's interior.
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Slightly more than an hour after transmission
from the probe ceased,
Galileo began its orbit insertion burn.
Its engine had to operate for 49 minutes
to put it into a highly elliptical equatorial orbit.
But this orbit would be altered with another burn
at its high point.
Mission designers were acutely aware
of the high radiation environment
and the second burn would lift Galileo
above the extreme radiation at its closest approach.
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Galileo's initial orbit
eventually delivered a close approach
to Ganymede, Jupiter's largest moon.
During this orbit,
engineers were trying to understand damage
to the spacecraft's vital tape recorder.
Without its high gain antenna,
the recorder was essential
for slow replay of data recorded
during the brief close encounters.
It had been stuck in rewind for 15 hours
and tape had been degraded.
Light emitting diodes, key elements
in the recorder's control system
had acquired radiation defects.
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The second orbit also paths Ganymede.
Galileo discovered it's the only moon in the solar system
with a significant magnetic field.
It also has an ocean sandwiched between two layers of ice.
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Galileo's orbits would be slightly varied,
so that it could make close approaches
to different Jovian moons.
But the equatorial orbits
needed to reach the moons,
also took the craft through hotspots
in Jupiter's radiation belts.
With the observations made by the Voyagers,
the moon Europa was of particular interest
to the Galileo team.
Data from several instruments agreed
that a salty ocean exists beneath Europa's surface ice.
Later examination of the Galileo data sets
revealed plasma wave and magnetic field information
showing that plumes of water vapor
were erupting from cracks in the surface.
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Europa has more water than Earth,
which makes it a possible home to life.
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Io was already known to have volcanic activity,
but Galileo saw tides in the moon's solid surface
of more than 100 meters.
The temperatures generated
by this gravitational distortion of Io
make its numerous volcanoes hotter
than anything found on Earth.
During its eight years at Jupiter,
Galileo completed 35 orbits
filling out our limited picture of the Jovian system.
This was never an easy mission.
Galileo was a robust spacecraft,
but the radiation environment stressed all the subsystems
and engineers were constantly having to find workarounds
for the frequent breakdowns Galileo suffered.
Instruments showed increased noise where near Jupiter
and current leakages caused by radiation
led to several resets of the onboard computer
with crucial loss of data.
Software changes enabled the computer
to recognize these resets
and to recover by itself.
Information learned would lead to changes
in the way the next Jupiter spacecraft was designed.
Five, four, three, two, one.
Ignition and liftoff of the Atlas V with Juno
on a track to Jupiter.
In August, 2011,
Juno began a journey to Jupiter
that would last almost five years.
Its mission parameters would be very different to Galileo's.
It would ignore the moons
and focus exclusively on Jupiter.
Spacecraft design, so crucial electronics shielded
within a thick titanium volt.
And rather than a plutonium power source,
Juno would rely on solar panels.
The sun's intensity at Jupiter is roughly 5%
of what it is at Earth
so the panels are huge.
A shortage in stocks of plutonium-238
led to the change in power sources.
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Juno followed a looping orbit
that took it beyond Mars
before swooping back to Earth for a gravitational boost
that added 14,000 kilometers per hour to its velocity,
sending it on to Jupiter.
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Juno approached Jupiter on a path
that took it above the planet's north pole.
It was destined for north-south orbit.
This would see it pass beneath the severest sections
of the planet's radiation belts
that extend out from Jupiter's equator.
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Four days before its closest approach,
mission control center command
that initiated the craft's autopilot.
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On July the fourth 2016,
Juno began an engine burn
that would insert it into a 53-day orbit.
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48 minutes later,
mission control at JPL received tones
verifying that Juno had started its deceleration maneuver.
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It was a tense 35-minute wait
from the systems engineers
before confirmation came through
that Juno had performed exactly as intended.
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(Juno roaring)
(crowd applauding)
For the Juno scientists and engineers,
it was a relief that things were going to plan.
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Juno is equipped with a suite of instruments
capable of penetrating Jupiter's thick cloud.
The polar orbit allows Juno
to compile a three-dimensional map of the upper atmosphere,
building a picture of the entire planet as it rotates.
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The images of Jupiter from this new perspective,
appear to come from a different planet.
Researchers were stunned.
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It was planned that Juno
would only make two 53-day orbits
and then change to a series of 14-day orbits
that would speed up the sampling rate.
(Juno hissing)
The spacecraft's main engine
is fueled by hydrazine and nitrogen tetroxide,
which ignites spontaneously when mixed.
The propellant and oxidizer are forced out
by a bladder of expanding helium.
As Juno was finishing its second orbit,
the helium valves were not responding correctly.
So it was decided to maintain the original orbit.
The mission extension has been granted
to allow for the longer orbits Juno continues to follow.
Within a day of the helium valve problem,
Juno went into safe mode.
All instruments went offline and data was lost.
It appeared to be similar
to the difficulties experienced by Galileo,
but engineers traced the issue
to a data transfer problem
from one specific instrument
and the spacecraft remains healthy.
Jupiter's axis is tilted at only three degrees
making even an oblique view of the poles near impossible
until Juno arrived.
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When viewed in the infrared,
researchers saw a complex arrangement of storms
at both the poles.
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At the north pole,
a central vortex is surrounded by eight anticyclones.
At the south pole,
five anticyclones surround the central storm.
Scientists do not understand why the storms
all rotating in the same direction,
do not obliterate each other.
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On its seventh close pass of Jupiter,
Juno flew directly over the giant Red Spot.
It's microwave radiometer
was able to map the heat distributions at varying levels
down to 350 kilometers.
The Red Spot is a giant storm
and Juno was able to see much higher temperatures
at the deepest levels they could penetrate.
With no geographic features as on Earth,
there is nothing on Jupiter
against which storms can dissipate.
The Great Red Spot remains firmly 22 degrees
below the equator.
Yet it appears to have drifted around the planet
at least 10 times since reliable observations began.
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Jupiter's magnetosphere is huge.
It traps charged particles in bands,
stretching out to vast distances.
This gives sensitive electronics
on orbiting spacecraft like Juno big problems.
It was assumed that Jupiter's magnetosphere
was generated like Earth's by dynamo action.
The convective movement
of an electrically conductive fluid deep within.
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So far, results from Juno suggests
that this is not the case.
The lumpy nature of Jupiter's magnetic field
points to an atmospheric source,
the giant auroras at the poles
also seem to come from a different mechanism
than here on Earth.
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By focusing on the composition of the gas giant,
researchers are hoping to gather clues
about conditions at the formation of the solar system.
While the Earth has been continuously changed
by tectonic forces,
it is thought that Jupiter
remains very similar in composition
to the cloud of gas and dust
from which the solar system was formed.
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At the end of its mission,
Juno will be sent on a collision course with Jupiter
to avoid any possible contamination of the delicate moons.
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The next mission to the Jovian system
will focus on Europa
as the most likely place after Earth
to harbor some form of life.
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Known as Europa Clipper,
it's scheduled to launch in 2022.
Like Juno, it will be solar powered
and it's elliptical orbit of Jupiter
will see it fly over Europa every two weeks.
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Early concepts for the mission
called for the inclusion of a lander.
But this idea was soon rejected as premature
because more needs to be learned
about the surface of the icy moon.
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Though Europa's ice crust is thought
to be at least 19 kilometers thick,
accurate measurements need to be made.
If thin areas can be found,
then future missions may be able to access the ocean
that lies beneath.
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Concepts for under-ice explorers are in development
and we can expect other missions
to focus on other moons.
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As the largest planet, Jupiter's influence
on the rest of the solar system is profound.
It has more than twice the mass
of every other planet combined.
All other planets' orbits are affected
by Jupiter's gravitation.
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There is still much to learn about Jupiter.
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