WEBVTT FILE

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TEXT ON SCREEN: NASA's Cassini
spacecraft arrived at Saturn in

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2004.

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TEXT ON SCREEN: Cassini studied
Saturn and its moons in the

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infrared using its
CIRS instrument.

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TEXT ON SCREEN: CIRS is an
infrared spectrometer built and

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operated by NASA's
Goddard Space Flight Center.

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TEXT ON SCREEN: Here are some
of Cassini CIRS' 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 lunchboxes.

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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 32 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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[ Satellite beeping ]