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Our solar system is vast.

From our own star the Sun to Earth
is nearly 150 million kilometers,

or one Astronomical Unit.

Jupiter is 5.2 AU distant
and Pluto up to 48 AU,

and the solar system extends far beyond
this into interstellar space.

We humans cannot travel
that sort of distance,

at least not yet.

But we can and do send
our robots and probes in our place,

and the results are astounding.

The ion-propelled Dawn spacecraft
is one of our emissaries

that has rendezvoused with two asteroid
belt objects in its multiyear mission.

The Dawn mission is one of
NASA's Discovery program missions

that launched in September of 2007.

So it's had a long circuitous journey
from the Earth,

flying past Mars
and out to the asteroid 4 Vesta,

where it spent a year
orbiting this small rocky object,

and mapped its surface
and determined its bulk composition

and geological aspects of Vesta

before leaving the gravitational field
of Vesta,

and traveling for another three years
out to the dwarf planet Ceres.

Before the arrival

of the spacecraft Dawn at Ceres,
we were expecting an inert rocky body.

Instead they discovered
a world of mystery and surprise.

Dawn has been orbiting Ceres
for more than two years now,

providing us with fascinating views
of an alien world.

The mysterious bright spots on Ceres
appear to be salts

deposited on the surface
by subterranean activity.

Support for this theory can be
found at another feature of interest:

the bright mountain, named Ahuna Mons.

We have been looking in detail
about the shape of the mountain

and we have compared with what we know
from volcanic constructs.

And we have found that Ahuna Mons' shape
is very similar to a volcanic dome

that is built
by very viscose material.

When we saw Ahuna Mons,
we saw that its shape was very tall.

It was very tall and had steep slopes.

And that reminded us

of certain places in the solar system,
including Earth and Mars,

that had domes that were formed
by volcanic activity

of very slow-moving thick material.

However, on Ceres,
the temperatures are so cold

that the same type of magma
on Earth and Mars

just can't exist on Ceres.

So we then concluded that the magma
or the material that's flowing on Ceres

had to be composed of mostly
very salty water

that would flow
at the low temperatures of Ceres,

and when exposed to the surface,

when they were pushed out
onto the surface,

they would freeze
and form this steep-sided dome.

Ahuna Mons is unique in the solar system.

There's no other place
in the solar system

that has a structure that matches that
of Ahuna Mons,

and it has to be formed
by cryovolcanic activity.

Scientists
at the German Aerospace Centre

have used stereo images

to create a global digital terrain map
of the dwarf planet.

Another surprise, a study published
by lead author Norbert Schorghofer

shows permanently shadowed regions
at the North Pole.

These are expected to be cold enough
to accumulate water ice

over long timespans.

Future spacecraft visiting Ceres
are likely to find freshwater ice there.

So right now we are not only
learning about dwarf planet Ceres,

but also about planets and small bodies
in the outer solar system,

like Pluto and its moon,

and so we are in a phase
in space exploration

where we are learning
about a new class of object,

and we are seeing
that these objects are surprising

as they have
recent features on their surface.

These observations tell us that
Ceres was active in the recent past

and might be even active today.

And this tells us the importance of
sending a spacecraft to a dwarf planet

to have a close look at the surface...

as we are learning new things
that are unexpected.

Dawn is now orbiting
only 386 kilometers above Ceres,

which is closer than the Space Station
is to Earth.

And it will continue
to return spectacular views.

One of the key technologies that made Dawn
such a success

was its ion drive.

Ion propulsion allows us
to undertake missions

which would be impossible without it.

There have been previous
missions and tests of ion propulsion

to validate the basic technology,
but Dawn now has made it a reality.

Dawn is the only spacecraft ever,
in more than 58 years of space exploration

to orbit two
extraterrestrial destinations,

the last unchartered worlds
in the inner solar system.

And it not only allows us
to get to these distant bodies,

but once we're in orbit,
we can maneuver extensively

in order to get the best possible science
that we can from the mission.

Our second deep space emissary

has only recently arrived
at its destination:

the giant planet Jupiter.

Juno is our fastest probe to date,

reaching a top speed
of 265,000 kilometers an hour

or 73.6 kilometers a second,

it has traveled for almost five years
to reach its target,

and orbits the poles
of the largest planet in the solar system.

Juno is the fastest
spacecraft ever to venture

into the outer solar system.

It's the first to orbit
pole to pole about Jupiter,

and it's the most heavily shielded
spacecraft that we've ever launched.

The mission is designed
to basically wrap Jupiter

in a dense net of observations,
completely covering the sphere. So to do that, we need a polar orbit,
one that passes over the North Pole,

along a line of longitude,
and over the South Pole.

And we do this over the 37 orbits
of the nominal mission,

and by the time we're done,
we've got orbits separated in longitude

by about every 12 degrees,
so we completely cover the sphere.

Basically the interior
of Jupiter is nearly unexplored.

What we see when we look at Jupiter,

and all the great, amazing stuff
we've discovered about Jupiter:

it's about the moons
that orbit the planet,

it's about the atmosphere,
and the enormous weather systems,

and the Great Red Spot,
and belts and zones,

you know, stripes across the planet.

All kinds of really cool,
interesting, exciting stuff,

but it's kind of skin deep.

When we look at Jupiter,
we're going a percent or two

of the way down into the planet.

That's what we're really seeing.

Everything else about Jupiter,
the deep interior of Jupiter,

is nearly completely unknown.

To peer beyond the veil

the suite of instruments onboard Juno
includes a gravity radio science system,

plasma and energetic particle detectors,

ultraviolet and infrared spectrometers,

and a vector magnetometer.

A magnetometer is,

it's best to think of it
as a fancy compass.

Unlike a compass that just records
the direction of the magnetic field,

our instrument tells you
both what direction the field is in,

and what the magnitude is.

And we can measure that
very, very accurately,

to a hundred parts per million.

Juno's magnetometer is another
in a long line of magnetometers

built here
at Goddard Space Flight Center,

following designs
developed by Mario Acuña years ago.

Our instrument is between one
and two orders of magnitude more accurate

than anything that's flown
to Jupiter before.

And, of course, part of that
is the result of the star cameras

that we're able to fly with our sensors,

so that we can determine the absolute
orientation in space of these sensors.

If we did not know
the orientation of the sensor

as well as we can determine it
with the star cameras,

we would lose accuracy
in the vector measurement.

So we carry four star cameras
with our two magnetometer sensors.

These have to be held in the same
orientation with respect to each other

under very extreme
environmental conditions.

So we designed what we call
"the magnetometer optical bench."

It's a special structure,
about a square foot in size,

that is made
of a carbon silicon carbide material,

almost impossible to machine,

but once it's fabricated
and the sensors are assembled,

they act as one.

And that's one of the reasons why we can
achieve much higher accuracy

than has ever been attempted before.

Studying the magnetosphere
of Jupiter is a prime objective.

Magnetic fields have been
a curiosity for thousands of years.

And so, of course, we know now
that magnetic fields are generated

by what's called dynamo action,

the convective motion of
an electrically conducting fluid.

Even though we can map
the Earth's magnetic field

with extraordinary accuracy,
with satellites in orbit about the Earth,

the one thing we can't do, is see clearly
through all the crustal magnetization

that is right beneath our feet.

Jupiter is a gaseous planet.

Hydrogen, helium, there is no magnetized
crust that obscures our view

of the dynamo deep below.

So the exciting part about the Jupiter
mission is that we'll be able to image,

for the first time, the magnetic field
on the dynamo's surface

in a way that would never ever
be possible on Earth.

Jupiter's also the planet
with the largest magnetic field.

Its magnetosphere is huge.

If you were to look up into the night sky,

and if you could see the outline
of its magnetosphere, which you can't,

it would be about the size
of the Moon in the sky.

It's a very, very large magnetosphere.

In fact, in the Voyager program
we learned that the magnetic tail,

the part of the magnetosphere
that is drawn away from the Sun,

extends all the way out to the orbit
of Saturn and, in all likelihood, beyond.

It's a very large feature
in our solar system.

It's a pity we can't see it.

Of course,
a strong magnetic field

traps more radiation within its grasp,
another issue for Juno.

There's two types
of radiation we worry about.

One is when we fly
through the radiation belt,

we get an instantaneous exposure.
We call that flux.

The other is

flying through the radiation belt
again and again and again

gives us something about accumulation.

We call that dose.

And so, in the beginning of the mission,
we fly largely close to the planet

underneath this flat donut-shaped
radiation belt,

and then we fly around it.

But eventually we fly
more and more through the belts

and our radiation levels every orbit
get worse and worse and worse.

We get over 80% of our radiation exposure
in the last half of the mission.

For me,
the great excitement is the opportunity

to look down and get the first clear,
unobstructed view

of what the magnetic field looks like
on the surface of a dynamo

where it's generated.

It's always incredible to be the
first person in the world to see anything.

We stand to be the first to be able
to look down upon the dynamo

and see it clearly for the first time.

Our emissary
to the ringed planet Saturn

is now in its final year of operation.

Its outstanding performance has included
dropping a probe on the moon Titan,

making extensive observations
of Saturn and its moons,

even adjusting its mission to fly
through the water vapor plumes

discovered gushing
into space from the moon Enceladus.

Cassini was never designed
to look for life in the Enceladus ocean,

but it does have
powerful instruments that can be used

to look for habitability.

So we're looking
for the conditions suitable for life.

Now, Enceladus is a tiny moon,
but it's really intriguing.

It's got this plume that is shooting out
from its south pole.

The plume is mostly comprised
of water, water-ice,

that gets frozen
when it's ejected out into space.

Most of these particles are coming
from these four major fractures

that we call tiger stripes.

Life needs three things, right?

It needs water, it needs chemistry,
and it needs energy.

And right now, some of these lines
of evidence are telling us

that Enceladus has these three things.

We see some salts,

but most importantly,
we see organic molecules,

things like methane.

We also see CO2, ammonia.

One of the things that Cassini
can look for is molecular hydrogen.

This is the smallest molecule
that exists in the universe.

It's two hydrogens bonded together.

This molecule can tell us about things
like hydrothermal activity

going on in the ocean of Enceladus.

And this is very important as we start
to answer that ultimate question of

"Is there really life on Enceladus?"

NASA’s Cassini mission has
begun a daring set of ring-grazing orbits,

skimming past the outside edge
of Saturn's main rings.

Cassini is flying closer to them
than it has since its arrival

over 12 years ago.

It will begin the closest study
of the rings

and offer unprecedented views of moons
orbiting near them. Even more dramatic orbits
will take Cassini through the F ring,

the outer and most active ring,

which contains one ring
and a spiral strand around it.

Cassini will make
its final orbit later this year

and plunge into the Saturnian atmosphere,

ending more than 11 years
of scientific observations.

Traveling over ten years
and 5.5 billion kilometers,

New Horizons is our emissary
to the outskirts of the solar system.

In a dramatic fly-by, New Horizons
scanned Pluto and its main moon Charon.

The brief encounter
amassed gigabytes of data,

which the spacecraft
took months to download to Earth.

Its close-up details of Pluto's terrain
generated a great many questions.

It looks more complex and highly active
geologically than first thought,

with solid nitrogen ice
forming many fascinating

and colorful textures and landscapes.

New Horizons captured
this high-resolution enhanced color view

of Charon just before closest approach.

Charon's color palette
is not as diverse as Pluto's.

Most striking is the reddish north polar
region, informally named Mordor Macula.

After such a successful fly-by,
the mission has extended

to include a second Kuiper belt encounter.

New Horizons is set to fly past
2014 MU69,

a Kuiper Belt Object currently
about 1.6 billion kilometers beyond Pluto.

Arrival time January 2019.

As one mission ends,
another is about to begin.

BepiColombo,
Europe’s first mission to Mercury,

is currently being put through its paces

at ESA’s European Space Research
and Technology Centre in the Netherlands.

BepiColombo consists of several components
in a so-called "spacecraft stack".

Apart from the two orbiters,
there’s also the Mercury Transfer Module, which contains the solar electric
propulsion engine to get them there.

Okay, what we have here is the MTM,

the Mercury Transfer Module,

which brings us or our two spacecraft
to Mercury,

the three xenon tanks
and the four thrusters.

And when we arrive at Mercury,
this unit will be jettisoned

and then we only have our two spacecraft.

The two spacecraft are ESA's
BepiColombo and the JAXA Magnetospheric Orbiter.

Mercury is the closest planet
to the Sun in our solar system. Yet despite temperatures reaching
around 500 degrees Celsius,

the previous NASA Messenger mission
found evidence for ice

at the planet’s north pole.

One spacecraft
is provided by ESA,

which is MPO, we call it MPO,
Mercury Planetary Orbiter,

and this spacecraft
has a focus more on the planet.

We want to observe the planet,
through remote sensing,

characterize the surface,
count the craters.

We are wanting to know
about the composition of the surface,

the interior of that planet.

And in addition we have
a second spacecraft,

and this spacecraft is called
the Mercury Magnetospheric Orbiter,

more focused on the environment,

and this spacecraft is provided
by the Japanese space agency.

The Messenger mission
found other surprises

at the smallest planet
in our solar system.

It discovered more chemical elements
and compounds with small boiling points,

known as volatiles,
than expected at the surface.

Messenger focused
on the north polar region,

whereas BepiColombo and its
instruments will cover the whole planet,

as well as exploring its gravity field.

One of special things
about Mercury is that it’s the only planet

besides Earth
with a magnetic dipole field.

And so we would like to understand
the dipole around Mercury

or how the magnetic field around Mercury
is interacting with the Sun.

And that’s very important for us
because then we can learn for Earth

how the Earth’s magnetic
field is interacting with the Sun.

And we have lot of satellites around
Earth which are affected by the solar wind

and the interaction,

so if we can get some clues
about processes on Mercury,

we want to learn for Earth.

BepiColombo’s launch has been
set back by minor hardware issues.

Now scheduled for late 2018 launch,

it is expected
to reach Mercury in 2025.

With the go-ahead from NASA,
the Europa Clipper mission is underway,

with the selection of instruments to fly
on the spacecraft

hopefully in the early 2020s.

Its mission is focused
on the Jovian moon Europa,

believed to hold an enormous
ocean of water beneath its icy surface.

Europa's proximity to Jupiter
and its speedy orbit

cause the moon to stretch
and contract under gravitational forces,

generating mechanical heat
within the core

and providing enough energy
to maintain a liquid ocean.

Close inspection of surface areas also
predicts that ice movement on the surface,

similar to glacial movements,

could allow for the formation of liquid
water lakes close to the surface. One more place to search
for those elusive signs of life.