[ Music ]
My name is Michael
Flasar and I am the principal
investigator of the Cassini
Composite Infrared Spectrometer,
otherwise known as CIRS.
My name is Conor Nixon.
I'm a planetary scientist here
at NASA's Goddard Space Flight
Center, and I study Saturn and
its amazing system of moons and
rings using the Composite
Infrared Spectrometer on the
Cassini spacecraft.
My name is Carrie Anderson.
I work at NASA's Goddard
Space Flight Center and I'm a
co-investigator
on the CIRS team.
Cassini is the mission that was
to study the Saturn system, and
has studied the Saturn system.
It consisted of a spacecraft
that orbits Saturn and studies
all the other satellites in
the system, and the rings.
But it also had a probe, and
its probe landed on Titan.
Before Cassini, the
previous flagship was Voyager.
That flew by the Saturn
system in 1980, Voyager 1.
In 1981 was Voyager 2.
Those were just flyby missions.
Cassini went into orbit around
Saturn, which was the first
time, very historical,
this had never happened.
Off-screen: And liftoff of
the Cassini spacecraft on a
billion-mile trek to Saturn!
The spacecraft launched in 1997
and after a long, seven-year
cruise, it arrived at Saturn,
did a dramatic entry burn into
orbit around Saturn, and
then commenced a wondrous,
thirteen-year mission to explore
the entire system of moons and
rings around Saturn.
CIRS is Cassini's Composite
Infrared Spectrometer, built at
NASA's Goddard Space Flight
Center, and this instrument is
designed to measure thermal
infrared radiation, or heat, and
split it up into different
wavelengths and measure the
intensity of each one
of these wavelengths.
The other thing is,
it's a chemical assayer.
These molecules in the
atmosphere, ethane, methane,
hydrogen, these molecules
have distinct signatures in the
spectrum.
They're their fingerprints.
TEXT ON SCREEN: After arriving
in 2004, Cassini began observing
Saturn and its moons in
the infrared using CIRS.
CIRS carried out
over 1.4 million commands and
collected terabytes of
data and image products.
Here are some of
the instrument's greatest hits.
So in 2010, there was a giant
outburst in Saturn's northern
hemisphere.
A giant storm eruption occurred,
and eventually this spread
around to encircle the entire
globe at a latitude width about
the extent of North America.
Imaging first picked it up,
and it was, it was massive.
From north to south it spanned
about nine thousand miles.
CIRS saw temperature increase
like we've never recorded
before.
CIRS, looking with its thermal
infrared eyes, was able to see
two bright beacons of hotspot
temperatures shining about 150
degrees brighter
than the surroundings.
We, all of a sudden we
had these two bright spots.
After a month or two they
merged, which was kind of
curious, and then it
persisted for another two years.
In fact, it persisted longer
than the tropospheric storm.
Typically on Saturn these occur
about every twenty to thirty
years, this is the sixth one
that's been seen since 1876.
And Cassini was lucky enough to
be there at the right place at
the right time to see
this storm eruption.
Mimas and Tethys are two of I
believe the last count was about
62 moons that Saturn has,
and these are examples of these
icy satellites, two of
Saturn's icy satellites.
When you just take images
with Cassini they look normal.
With Mimas it looks like the
Death Star, you know, and then
you superimpose the
thermal maps from CIRS on it.
And when you superimpose the
thermal maps, it looks like
Pac-Man.
Mimas was an example where
we saw very warm temperatures
surrounding a very cold region,
as if it was going to, you know,
chomp it up.
Turns out the explanation
is kind of, is interesting.
The way these are created is due
to their orbital orientation as
they go around Saturn.
They have a leading side, which
is always towards the front of
its motion, and a trailing side.
And the leading side is
intensely bombarded by radiation
from Saturn's magnetosphere.
So the high-energy particle
bombardment is causing this
fluffy surface, this icy, fluffy
surface, to be packed down to a
very hard, solid ice surface,
and you're changing the way now
the surface can heat up and cool
down over the course of a day
for these moons.
When we look at these in
infrared we see a cooler region
on the leading hemisphere, and
a warmer region surrounding it.
And this gives the exact
appearance of these Pac-Man
features that we
so know and love.
Enceladus is a very
small, icy moon of Saturn.
It's about three
hundred miles in diameter.
It's a moon that we weren't
expecting to see a lot from, and
it's had a huge impact
on the Saturn system.
Previously, we had hints
that this moon may be active
stretching all the way
back to the Voyager mission.
But when Cassini arrived, it was
able to detect curtains of icy
material venting into space.
Then using the CIRS instrument,
we were able to zoom in on the
south pole, and see the south
pole was much warmer than we
expected.
The pattern of temperatures on
Enceladus did not match a simple
inert body absorbing
sunlight and reradiating it.
The question was what
to make of all this.
The community decided it must be
tidal friction, tidal heating,
as Enceladus orbits Saturn.
This tells us that Enceladus is
being heated up by the action of
Saturn's gravity.
Inside Enceladus, we now know
that there's a liquid water
ocean, and it's this ocean which
is venting through these cracks
into space.
Throughout the mission,
we've learned that it has a
subsurface,
liquid-water environment.
And with NASA, when you see
liquid water, it's "Follow the
water," because
that's important for life.
Titan was one of the
major objectives of Cassini.
We knew from Voyager that
Titan was an organic molecule
paradise, it just was
filled with organic molecules.
But maybe one of the key things
about Cassini was, instead of a
flyby past the Saturn system,
Cassini hung around for thirteen
years.
And during that time, even
though we were orbiting Saturn,
we flew by Titan a
hundred and twenty-five times.
Titan, at visible wavelengths,
looks like as everyone has seen,
a orange-y, hazy moon.
When Cassini was built, we put
on spectrometers that could see
to longer wavelengths, outside
of the eye's visible range.
And so we removed the veil of
this smog, we peeled it back.
Lo and behold, we saw this
amazing, very active surface.
River channels, and dunes,
and we found polar lakes.
And we never saw this before
because we couldn't penetrate
this very opaque,
hazy atmosphere.
In 2013, we made a fascinating
discovery about Titan's
atmosphere.
We discovered a new molecule,
which hadn't been previously
detected.
And this is called propylene,
and this molecule, on the Earth,
serves a variety of purposes.
In fact, it's one of the raw
ingredients that we use to make
a type of hard rubbery plastic
commonly known as Tupperware,
which we use in our lunch boxes.
And it was really incredible to
find this molecule just floating
around in Titan's atmosphere.
Going all the way back to the
Voyager mission thirty-two years
earlier, we'd seen a lighter
molecule and a heavier molecule
in the same chemical family.
But there was a gap at a
particular molecular mass, a
particular size of molecule that
we just couldn't see anything
in.
So this discovery, using CIRS,
filled in this puzzle piece,
which had been completely
outstanding for about thirty-two
years.
Cassini's Grand Finale is now
underway as we dive repeatedly
over the planet's north pole,
and through the gap between the
planet and its innermost rings.
We're making gravity
measurements and magnetic field
measurements, and this is
information that we didn't get
earlier in the mission so in
many ways it's like having a
whole new spacecraft mission.
Finally, on the very last orbit,
Cassini will go closer to Saturn
and eventually burn up
in its upper atmosphere.
The spacecraft will disintegrate
and become a permanent part of
Saturn.
It's a
bittersweet moment for us.
We're so used to doing
Cassini, we'll miss it.
As far as what CIRS has
accomplished, the excitement
about the Enceladus
south pole has to rank high.
The complex dynamics of
Saturn and its storms.
Titan, just being
able to see Titan.
The point is that if you don't
go up close and take the data,
you get nothing.
If you do take the data, there's
no guarantee you're going to
solve all the problems, but on
the other hand at least you've
made the effort to
acquire something and to ask
other questions.
This mission, and the amount of
data it's recorded, goes beyond
just one object.
Titan has always been my true
love, but I also have learned to,,
really appreciate other moons
in Saturn's system, for example,
Iapetus.
It has this amazing dark-leading
hemisphere, but its trailing
hemisphere is bright like snow.
It's been called the
yin and yang moon.
One of the moons called
Pan, it's embedded in Saturn's
A-Ring, and it causes this gap.
Pan looks like a flying saucer.
These kind of things, you can't
have unless you're in orbit
around such a
magnificent planet.
And the data we've taken from
this system, I have no doubt
will be used for decades to
come, and I only hope we can go
back one day.
[ Music ]
[ Satellite beeping ]
