WEBVTT FILE

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[ Music ]

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My name is Michael
Flasar and I am the principal

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investigator of the Cassini
Composite Infrared Spectrometer,

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otherwise known as CIRS.

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My name is Conor Nixon.

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I'm a planetary scientist here
at NASA Goddard Space Flight

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Center, and I study Saturn and
its amazing system of moons and

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rings using the Composite
Infrared Spectrometer on the

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Cassini spacecraft.

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My name is Carrie Anderson.

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I work at NASA Goddard
Space Flight Center and I'm a

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co-investigator
on the CIRS team.

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Cassini is the mission that was
to study the Saturn system, and

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has studied the Saturn system.

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It consisted of a spacecraft
that orbits Saturn and studies

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all the other satellites in
the system, and the rings.

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But it also had a probe, and
its probe landed on Titan.

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Before Cassini, the
previous flagship was Voyager.

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That flew by the Saturn
system in 1980, Voyager 1.

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In 1981 was Voyager 2.

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Those were just flyby missions.

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Cassini went into orbit around
Saturn, which was the first

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time, very historical,
this had never happened.

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Off-screen: And liftoff of
the Cassini spacecraft on a

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billion-mile trek to Saturn!

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The spacecraft launched in 1997
and after a long, seven-year

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cruise, it arrived at Saturn,
did a dramatic entry burn into

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orbit around Saturn, and
then commenced a wondrous,

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thirteen-year mission to explore
the entire system of moons and

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rings around Saturn.

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CIRS is Cassini's Composite
Infrared Spectrometer, built at

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NASA Goddard Space Flight
Center, and this instrument is

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designed to measure thermal
infrared radiation, or heat, and

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split it up into different
wavelengths and measure the

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intensity of each one
of these wavelengths.

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The other thing is,
it's a chemical assayer.

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These molecules in the
atmosphere, ethane, methane,

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hydrogen, these molecules
have distinct signatures in the

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spectrum.

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They're their fingerprints.

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TEXT ON SCREEN: After arriving
in 2004, Cassini began observing

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Saturn and its moons in
the infrared using CIRS.

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CIRS carried out
over 1.4 million commands and

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collected terabytes of
data and image products.

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Here are some of
the instrument's Greatest Hits.

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So in 2010, there was a giant
outburst in Saturn's northern

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hemisphere.

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A giant storm eruption occurred,
and eventually this spread

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around to encircle the entire
globe at a latitude width about

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the extent of North America.

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Imaging first picked it up,
and it was, it was massive.

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From north to south it spanned
about nine thousand miles.

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CIRS saw temperature increase
like we've never recorded

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before.

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CIRS, looking with its thermal
infrared eyes, was able to see

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two bright beacons of hotspot
temperatures shining about 150

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degrees brighter
than the surroundings.

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We, all of a sudden we
had these two bright spots.

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After a month or two they
merged, which was kind of

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curious, and then it
persisted for another two years.

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In fact, it persisted longer
than the tropospheric storm.

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Typically on Saturn these occur
about every twenty to thirty

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years, this is the sixth one
that's been seen since 1876.

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And Cassini was lucky enough to
be there at the right place at

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the right time to see
this storm eruption.

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Mimas and Tethys are two of I
believe the last count was about

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sixty-two moons that Saturn has,
and these are examples of these

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icy satellites, two of
Saturn's icy satellites.

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When you just take images
with Cassini they look normal.

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With Mimas it looks like the
Death Star, you know, and then

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you superimpose the
thermal maps from CIRS on it.

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And when you superimpose the
thermal maps, it looks like

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Pac-Man.

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Mimas was an example where
we saw very warm temperatures

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surrounding a very cold region,
as if it was going to, you know,

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chomp it up.

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Turns out the explanation
is kind of, is interesting.

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The way these are created is due
to their orbital orientation as

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they go around Saturn.

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They have a leading side, which
is always towards the front of

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its motion, and a trailing side.

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And the leading side is
intensely bombarded by radiation

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from Saturn's magnetosphere.

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So the high-energy particle
bombardment is causing this

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fluffy surface, this icy, fluffy
surface, to be packed down to a

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very hard, solid ice surface,
and you're changing the way now

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the surface can heat up and cool
down over the course of a day

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for these moons.

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When we look at these in
infrared we see a cooler region

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on the leading hemisphere, and
a warmer region surrounding it.

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And this gives the exact
appearance of these Pac-Man

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features that we
so know and love.

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Enceladus is a very
small, icy moon of Saturn.

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It's about three
hundred miles in diameter.

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It's a moon that we weren't
expecting to see a lot from, and

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it's had a huge impact
on the Saturn system.

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Previously, we had hints
that this moon may be active

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stretching all the way
back to the Voyager mission.

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But when Cassini arrived, it was
able to detect curtains of icy

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material venting into space.

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Then using the CIRS instrument,
we were able to zoom in on the

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south pole, and see the south
pole was much warmer than we

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expected.

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The pattern of temperatures on
Enceladus did not match a simple

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inert body absorbing
sunlight and reradiating it.

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The question was what
to make of all this.

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The community decided it must be
tidal friction, tidal heating,

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as Enceladus orbits Saturn.

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This tells us that Enceladus is
being heated up by the action of

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Saturn's gravity.

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Inside Enceladus, we now know
that there's a liquid water

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ocean, and it's this ocean which
is venting through these cracks

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into space.

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Throughout the mission,
we've learned that it has a

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subsurface,
liquid-water environment.

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And with NASA, when you see
liquid water, it's "Follow the

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water," because
that's important for life.

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Titan was one of the
major objectives of Cassini.

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We knew from Voyager that
Titan was an organic molecule

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paradise, it just was
filled with organic molecules.

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But maybe one of the key things
about Cassini was, instead of a

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flyby past the Saturn system,
Cassini hung around for thirteen

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years.

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And during that time, even
though we were orbiting Saturn,

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we flew by Titan a
hundred and twenty-five times.

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Titan, at visible wavelengths,
looks like as everyone has seen,

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a orange-y, hazy moon.

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When Cassini was built, we put
on spectrometers that could see

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to longer wavelengths, outside
of the eye's visible range.

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And so we removed the veil of
this smog, we peeled it back.

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Lo and behold, we saw this
amazing, very active surface.

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River channels, and dunes,
and we found polar lakes.

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And we never saw this before
because we couldn't penetrate

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this very opaque,
hazy atmosphere.

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In 2013, we made a fascinating
discovery about Titan's

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atmosphere.

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We discovered a new molecule,
which hadn't been previously

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detected.

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And this is called propylene,
and this molecule, on the Earth,

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serves a variety of purposes.

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In fact, it's one of the raw
ingredients that we use to make

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a type of hard rubbery plastic
commonly known as Tupperware,

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which we use in our lunch boxes.

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And it was really incredible to
find this molecule just floating

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around in Titan's atmosphere.

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Going all the way back to the
Voyager mission thirty-two years

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earlier, we'd seen a lighter
molecule and a heavier molecule

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in the same chemical family.

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But there was a gap at a
particular molecular mass, a

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particular size of molecule that
we just couldn't see anything

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in.

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So this discovery, using CIRS,
filled in this puzzle piece,

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which had been completely
outstanding for about thirty-two

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years.

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Cassini's Grand Finale is now
underway as we dive repeatedly

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over the planet's north pole,
and through the gap between the

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planet and its innermost rings.

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We're making gravity
measurements and magnetic field

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measurements, and this is
information that we didn't get

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earlier in the mission so in
many ways it's like having a

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whole new spacecraft mission.

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Finally, on the very last orbit,
Cassini will go closer to Saturn

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and eventually burn up
in its upper atmosphere.

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The spacecraft will disintegrate
and become a permanent part of

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Saturn.

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It's a
bittersweet moment for us.

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We're so used to doing
Cassini, we'll miss it.

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As far as what CIRS has
accomplished, the excitement

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about the Enceladus
south pole has to rank high.

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The complex dynamics of
Saturn and its storms.

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Titan, just being
able to see Titan.

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The point is that if you don't
go up close and take the data,

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you get nothing.

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If you do take the data, there's
no guarantee you're going to

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solve all the problems, but on
the other hand at least you've

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made the effort to
acquire something and to ask

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other questions.

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This mission and the amount of
data it's recorded goes beyond

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just one object.

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Titan has always been my true
love, but I also have learned to

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really appreciate other moons
in Saturn's system, for example,

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Iapetus.

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It has this amazing dark-leading
hemisphere, but its trailing

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hemisphere is bright like snow.

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It's been called the
yin and yang moon.

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One of the moons called
Pan, it's embedded in Saturn's

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A-Ring, and it causes this gap.

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Pan looks like a flying saucer.

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These kind of things, you can't
have unless you're in orbit

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around such a
magnificent planet.

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And the data we've taken from
this system, I have no doubt

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will be used for decades to
come, and I only hope we can go

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back one day.

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[ Music ]

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[ Satellite beeping ]