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Linda: Ten years ago today, the Cassini spacecraft
flawlessly executed a nail-biting 96 minute burn
to become the first man-made object
to go into orbit around Saturn.
And Cassini carried with it ESA's Huygens Probe,
which we later sent down to the surface of Titan.
And so we celebrate today
Cassini's ten-year anniversary,
and I'll share with you just a few
of the amazing findings that we've made with Cassini.
What we have here is one of my
favorite pictures of Saturn and the rings.
It's a view that you won't see from the Earth.
Cassini is high above Saturn's north pole looking down
and the rings form a giant bulls-eye around the planet.
And you can actually see Saturn's shadow
going out across the rings.
Up on the north pole, you see a greenish six-sided area.
We call this the hexagon.
Very interesting and intriguing kind of storm.
Saturn is the second-largest planet
in our solar system.
It only has pretty much a hydrogen atmosphere,
no solid surface underneath it.
And if you could build a bathtub
big enough to hold Saturn,
Saturn would float.
So how big is Saturn really?
Well if we put the Earth and the moon to scale,
next to Saturn, along with the distance between them,
we can see that Saturn is indeed huge.
In fact, it would take 764 Earths to fill up
the volume of Saturn,
a giant planet, indeed.
Well let's look a little bit more closely
at that north polar hexagon.
If you look at the image on your left,
you can see this greenish area surrounded by
a six-sided jet stream.
Voyager, 30 years ago, saw this jet stream
with these six sides, and it's still there today.
It's a very interesting puzzle.
Greenish in color, that's its winter hemisphere.
As the sun continues to shine in the north,
we'll see that greenish color become more of
the golden color we're used to for Saturn's atmosphere.
Tiny white clouds circle inside the hexagon.
And Cassini discovered at the very
center of the hexagon a giant hurricane.
That hurricane would span half
the continental United States.
It would go from Washington, D.C.
to Tulsa, Oklahoma: a giant storm.
The sun is shining from the right,
and you can actually see shadows from
the eyewall of that giant hurricane.
We study the hexagon and the hurricane at Saturn
to get a better understanding
of the weather here on the Earth.
Let's move on to Saturn's rings.
I actually started working on rings
in the Voyager days.
And so they hold a special place in my heart.
There's a lot of intricate detailed structure
inside of the rings.
The rings are made up of billions upon billions
of icy particles orbiting Saturn
in an intricate cosmic dance.
And every once in a while these particles
jostle and run into one another.
The rings have very simple names.
As you go outward, you can have, you can see
you have the A ring on your far right.
Then there's a gap, the very bright B ring,
most of the particles are there.
The particles range in size from tiny marbles
to giant mountain-sized particles.
That grayish ring is the C ring,
and then finally the innermost ring, the D ring.
And at the end of the mission,
Cassini is gonna dive in between Saturn's D ring
and the top of the atmosphere
for some remarkable brand new science.
You'll notice that there's a black gap
in between the A ring and the B ring.
That's the Cassini division,
named after the astronomer Cassini,
who first discovered it, and our mission
is named in honor of that astronomer.
Well, Cassini had a rare opportunity in 2009.
We were actually able to observe the rings
when the Sun was edge on to them.
And anything that would cast a shadow
would be visible and seen.
So let's look at the outer edge of the B ring
and see what Cassini saw in 2009.
Here's the outer edge of the B ring,
that bright ring with all of those structures,
the Cassini division on top.
The Sun is shining from the top down,
and you can see all sorts of shadows.
Here are particles that are one or two miles in size
casting these long shadows at the edge of the ring.
And the ring itself is only about 30 feet thick.
A good analogy for how we see these shadows.
Imagine yourself riding along on the space station.
You look down on Egypt,
and you want to find the pyramids.
But if you look at noon, you won't see any shadows,
and it'll be very hard to pick them out.
Now imagine that you look for these
same pyramids at sunset.
And they'll be casting these long shadows.
And they'll be very easy to see
on the desert in Egypt.
And in the same way, Cassini for the first time
could see that there were big particles in the rings
at the outer edge of the B ring.
These objects are probably made of
agglomerations of ring particles.
And the way these come together and coalesce,
give us information about how the planets
in our solar system actually came together
and formed as well.
This is a view of the largest moon
in the Saturn system.
This is giant Titan.
It's 3,000 miles across,
about the size of the planet Mercury.
A Titan has a liquid water ocean
underneath its icy crust, and this is one
possible place that might harbor life.
Titan has a thick nitrogen atmosphere.
It's about four times as dense
as the atmosphere in this room.
And the surface is a chilly
minus 290 degrees Fahrenheit.
There's also methane in the atmosphere of Titan,
and that methane at the top is broken apart
by sunlight, forms these long smoggy hydrocarbons
and gives Titan that sort of golden-colored haze.
And we can't really see through the haze.
And it took ESA's Huygens Probe
to parachute down through to the surface of Titan
to give us our first view of an amazing world.
It turns out that methane plays the same role
on Titan that water plays here on the Earth,
with the same kind of weather.
Only now you have methane clouds.
Methane rain.
Methane flowing through the river channels,
and methane filling the lakes and seas.
In fact, if you look at this image behind me,
that topmost black smudge, that's Ligeia Mare,
the second-largest sea on Titan.
And if we look up close at that particular sea,
here's the radar view with the long wavelengths.
You can penetrate down through the haze.
You can see the river channels of methane
flowing into this particular lake,
and even tiny islands in this particular sea.
This, this sea Ligeia Mare is about 50 percent
bigger than Lake Superior here on the Earth.
And it's about 500 feet deep.
That's something we found out with Cassini.
And if you take the seas and you add up
all the hydrocarbons that are present in the seas,
it turns out there's about a hundred times
more hydrocarbons on Titan
than all of the reservoirs here on the Earth.
It's just too bad Titan's so far away,
or our hydrocarbon problems would be solved.
( laughter )
And the seas themselves are very interesting,
because you wonder, with liquid methane,
could a form of life exist that would use
liquid methane, rather than water,
to form and move about.
So very intriguing to think about that for Titan.
Now we move on to another world,
another moon around Saturn.
This is Enceladus.
Enceladus is only about 300 miles across.
So 1/10th the size of Titan.
And what you see here is an icy white surface
with very few craters.
And the brightness and the absence of craters
tell us that this is a very, very young surface.
And Cassini was the first to see,
at the south pole you can see these
bluish fractures down here at the bottom.
We nicknamed them tiger stripes.
They kind of reminded us of tiger stripes,
and we were really amazed to see what was
coming out of these tiger stripes on this tiny moon.
I was amazed as everyone else when we first
took a look and saw, and this is in a backlit view,
coming out of those tiger stripes were jets.
Jets of water vapor and water ice
with some other compounds mixed in.
We saw dozens and dozens of these jets
actively going off.
Some of the tiniest particles escape
and actually go on to form a ring
within Enceladus' orbit, the E ring.
So just so intriguing to see.
In fact, Cassini actually flew through
those jets and sampled their composition.
And we found carbon dioxide, we found ammonia,
we found salts.
We found the kinds of ingredients
that you'd need to find to have life.
And it turns out there's a liquid water ocean
underneath Enceladus' south pole
supplying these jets and vents.
And in a sense we have free samples.
We just don't know if there might be life
inside of these free samples.
So we have two worlds: Titan and Enceladus,
that might possibly have life.
And finally, another iconic backlit image.
This image was taken when Cassini
was in Saturn's shadow.
This doesn't happen very often in the mission.
When we took this mosaic, that bluish ring
around the outside, that's the E ring
created by tiny particles coming from Enceladus.
And if you look at that white ring
completely around Saturn,
sunlight is refracted through the atmosphere.
And that's every sunrise and sunset on Saturn
seen all at the same time.
And there's actually three other planets
in this image.
If you look at the upper left there,
Mars and Venus, a little bit difficult to see.
And if you just look here, right here,
that tiny pale blue dot is actually the Earth,
actually the Earth and the moon.
And when, in the 20 minutes we were taking
those pictures of the Earth and the moon,
we actually asked people, "Go outside.
Wave at Saturn."
( laughter )
So your photons can be captured by Cassini
in these pictures of the Earth and the moon.
And while you're at it, out there waving,
in fact, how many people here waved at Saturn
on that particular day?
Well that's great.
Yeah, my husband Tom and I were out there
waving as well.
And we asked people to take pictures of themselves,
selfies, and send us those selfies.
And we took all of those selfies and we recreated
this Saturn backlit mosaic.
Here it is.
( laughter )
Made up of thousands of selfies.
So we were really happy to see all of the interest
that the public had, and we're very grateful
to NASA for continuing to fund extended missions.
It's been 10 years.
We hope to have another three years
to our mission as well.
And very recently we had a naming contest.
We asked people, you know, we've got this
exciting 22 orbits at the end of our mission,
help us name those orbits.
And then we got 2,000 different entries,
sorted through those, and we came up with
the winning entry.
And I'm pleased to present
for the very first time tonight,
the winner of that naming contest.
Cassini Grand Finale.
( laughter )
So thank you so much for your contributions.
And that's the name of the end of our mission.
And I'm gonna be showing you a short movie
that'll show you something about
the science we'll be collecting in the last three years,
including a chance to see what one of those
orbits look like in the Grand Finale.
And with Cassini, we had a rare opportunity
and we seized it.
Now sit back and enjoy the movie.
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Voiceover:
in the Saturn system now.
It has been making discoveries
for the last several years, and there's more to come.
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Voiceover:
in this Saturnian system, we begin to understand
something also about the origin of the solar system.
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Voiceover:
that most of the surface of Titan
is in fact covered with organic material of some kind.
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Voiceover:
lakes on the surface of this moon in detail.
We're gonna be looking at the atmosphere
to see how the climate changes over time.
Voiceover:
that tell us if the winds pick up.
We think there could be waves
on the lakes of liquid methane.
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Voiceover:
that we would discover active cryovolcanism
on one of these moons?
Geysers?
Voiceover:
in the next couple of years is make the first ever
flyby through the plume when the plume output
is at its maximum.
Voiceover:
there's the planet Saturn itself.
As we go through our series of orbits
and as the seasons change,
it's like having a brand new mission.
Voiceover:
is nearly 30 Earth years.
To be there for nearly half of a Saturn year,
is a once-in-a-lifetime opportunity.
Voiceover:
on the north pole.
So we're getting to see territory
that was darkness when we first arrived in 2004.
Pretty soon we'll have the whole hexagon
and the hurricane inside of it illuminated by the sun.
And then of course the mission's end itself
is completely unique.
Voiceover:
these orbits will take us up and over
the north and south poles of the planet.
Voiceover:
to dive in between the innermost edge of the D ring
and the upper atmosphere of the planet itself.
Voiceover:
how is Saturn constructed from inside out.
Voiceover:
of the planet, the mass of the rings
for the very first time,
and get to sample a place that no spacecraft
has ever flown before.
Voiceover:
that cannot be duplicated.
So we really want to take advantage of this
opportunity to observe seasonal variation
in the system.
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