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Practice English Speaking&Listening with: The First 1000 Days: Cassini Explores The Saturn System

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LESLIE: Good afternoon, ladies and gentlemen.

Today we're privileged to have with us Dr. Carolyn Porco, who

is the leader of the Imaging Science Team

on the Cassini Mission.

And she is also an imaging scientist for the New Horizons

Mission, which is also a post that she held as well for the

Voyager Mission.

She's received her doctorate degree from the California

Institute of Technology in the Division of Geological and

Planetary Sciences, and she's a tenured faculty member with

the University of Arizona.

She's the editor and creator of the Cassini Team CICLOPS

website, which is where you can view images from the

Cassini Mission.

And she's also the CEO of Diamond Sky Productions, a

small company dedicated the artful and useful use of

planetary images.

Asteroid number 7,231 is named in her honor, and she's

responsible for sending the remains of renowned planetary

geologist, Eugene Schumacher, to the moon.

Please join me in welcoming Dr. Porco.

DR. CAROLYN PORCO: Thank you very much.

Is there any way we can lower the lights in this room

because the pictures will look so much better if the lights

can be lowered.

Thank you, Leslie, for that introduction.

I just want to say, ever since the TED conference--

I don't know if you guys know about the TED conference.

You must, because it sort of happens in your backyard,

where I met Larry and Sergey, and I got invited to come to

give a talk here.

I've been really looking forward to coming here, and

this place is kind of legendary.

The cafes are legendary, and I've now sampled the cafes.

I know what that's all about.

And there's something I know is going to be legendary soon,

and I just sampled it, but I never knew about it.

And that is your heated toilet seats.

You do realize the rest of the world doesn't live like that.

OK, and I can tell you that's one perk you're not going to

find at NASA.

So anyway, it's a thrill.

It's even more of a thrill than I thought to be here.

I feel that I have lived a charmed existence to have

grown up during a time when I did.

I was a young girl when our country became

a spacefaring nation.

And images from the moon, and Venus, and Mars were being

sent back to Earth and being published in the newspapers of

New York, which is where I grew up.

I was a teenager when Neil Armstrong first walked on the

moon in 1969.

I was a young graduate student when the Viking Spacecraft

landed on Mars in 1976.

And I was a senior graduate student when the Voyager

Spacecraft first flew by Saturn in the early 1980s.

A newly minted PhD, I became part of the Voyager Imaging

Team in 1984, '83 and participated in our first

reconnaissance of the planets Uranus and Neptune.

And now I'm extraordinarily privileged to be part of one

of the most dazzling interplanetary endeavors we

have ever undertaken.

And I've got, as far as I'm concerned, the best job in the

whole inner solar system.

I am the leader of the Imaging Team on Cassini.

We are responsible for taking all those lovely images of

Saturn that you've seen over the last several years.

And these missions of exploration that humankind has

been undertaking for the last 50 years, I think you would

agree, are all part of a much larger human quest, or human

voyage, to come to understand something about our origins,

and how our planet, we living on it, came to be.

And one of the most promising places we could hope to

explore in our solar system, an answer to those questions,

is the Saturn system.

Because Saturn with its complex systems, subsystems,

if you will, of atmosphere, magnetosphere, rings, and

moons all interacting provides the ideal destination for

studying many of the same physical processes that

planetary scientists today believe were responsible for

the formation of the solar system, and are responsible

and ongoing today for the present day dynamics of our

solar system and solar systems around other stars that are

being discovered in our galaxy.

So aside from offering splendor and beauty beyond

compare, Saturn is one planetary system whose

exploration offers enormous cosmic reach.

We, of course, had been to Saturn with the Pioneer

Spacecraft in the voyages in the early 1980s, but our

investigation of this planetary system began in

exquisite detail when in the summer of 2004, the Cassini

Spacecraft flawlessly glided into orbit around Saturn and

became, at that point, the farthest robotic outpost that

humanity had ever established around the sun.

And for me, our return to this particular planetary system is

not only part of, but also a metaphor, for that grander

human voyage to come to understand the

interconnectedness of everything surrounding us.

So I'm thrilled to be able to tell you this afternoon, to

show you how this particular leg of this voyage, this grand

voyage, through the Saturn system, as Cassini is

revealing it to us, is how Saturn and everything around

it has been shown to us over the last 1,000 days that

Cassini has been in orbit.

And to give you a sense, and a decidedly visual one at that,

for how this very major exploratory expedition that

Cassini, and we, are presently conducting around Saturn is


The first obvious example of cosmic reach, of course, of

Saturn's rings, they're the reason why Saturn is the icon.

It is among planets in our solar system.

The rings are a tremendous visual spectacle.

They are 280,000 kilometers across.

That is about one light second.

They would fit in nicely between the

Earth and the moon.

And they consist of countless orbiting bodies.

This is ice particles ranging in size from the finest snow

you might ski on in Utah, all the way to the sizes of small

apartment buildings, screaming around Saturn at tens of

thousands of miles per hour yet only very gently jostling

each other.

They only collide, if and when they do, at a few millimeters

per second.

They are what physicists call a very equillibrated system.

Any violent collisions in the system died

out a long time ago.

And because of that, they are tremendously thin.

They're only one, two, three stories in

a modern day building.

They're paper thin.

They're very mathematically precise.

They trace out the plane, have gravitational equilibrium

around the planet.

And despite their visual enormity, they contain, in

fact, comparatively speaking, very little mass.

If you took all the mass in Saturn's rings and recomposed

it back into a small moon of the proper density, it would

be no bigger than this little moon here, Enceladus, so a lot

of visual display for very little mass.

Is there a laser pointer I can get a hold of, somebody?

OK, the processes that are ongoing in this disk--

OK, thank you.

There's 47 buttons on this.

I hope I hit the right one.

By the way, these are the shadows of the rings cast on

the northern hemisphere of the planet.

And the processes that are ongoing in this disk of

material are believed to be similar or identical to the

ones that went on in the nebula from which the sun and

the planets form-- this is shown here in this artist's


and in disks that we are presently seeing

around other stars.

This is a Hubble Space Telescope picture of a

protostellar disk around a very young M-dwarf star.

And then reaching a trillion times larger, the same

processes we see going on in Saturn's rings occur in the

disks of dust, and gas, and stars that

are the spiral galaxies.

So there is a great deal to be learned in studying Saturn's

rings about disk systems all throughout the cosmos.

And in this sense, what we are learning, and hope to learn

further with Cassini, is truly universal.

The rings exhibit an enormous variety of structure

discovered a long time ago when the

Voyagers first flew by.

We didn't understand where most of it came from, and

we're only now getting glimmers of it with Cassini.

They break down, some of you may already know, into three

main elements.

This is the A, the B, and the C ring.

The B ring is the most massive.

It's the densest. It casts the deepest, darkest shadows on

the planet.

It's where a lot of this structure is that we are

having a hard time understanding.

The A ring is a little bit more transparent.

It's punctuated by gravity-driven features that

are driven by the gravity of orbiting moons.

And then here is the C ring, which is very diaphonous, and

is actually populated by these very

sharp-edged plateaus of material.

Again, we don't know exactly why, we don't know, in fact,

at all why those plateaus exist. And so the subtle

colorations you see here are due to the contamination of

basically what is water ice by very small

amounts of other materials.

And we're in the process of working out what the

composition of that material is.

So Saturn is, as you know, very far away.

It's ten times farther away from the sun

than the Earth is.

And the Cassini Spacecraft at launch was very massive.

It was six metric tons.

And even launching Cassini on the largest launch vehicle

that we had at the time, which was a Titan IV, adding solid

rocket motors to it, strapping those on, and putting Cassini

on top of the Centaur upper stage-- this was about as much

power as we could throw at the thing-- that still wasn't

enough to get Cassini, because it was so

massive, directly to Saturn.

So we had to loop it around the inner solar system twice.

We had to send it by Venus twice.

We had to send it by the Earth once.

And then finally on the eve of the year 2001, which I thought

was tremendously poetic, we sent it by Jupiter for a final

push on to Saturn.

Now understand that the object of this exercise is to get the

spacecraft to its target as quickly as possible so that

those of us who are involved in the mission are still alive

by the time the spacecraft gets there.

But that means that by the time it gets

there, it is hauling.

And we actually have to slow it down in order to allow it

to get captured into Saturn orbit.

And that was done in a 19-minute maneuver, shown here

in an artist's depiction, where we basically threw the

engines in reverse.

Actually we didn't do that.

We just turned the spacecraft around.

Half of the mass at launch of Cassini was fuel that was

burned in this maneuver to slow it down.

We didn't slow the speed down.

We actually slowed the acceleration down to allow it

to get captured into orbit.

And so this maneuver brought us closer to the rings than we

had ever been before, will ever get again, very likely

never be as close as we were during this maneuver ever

again in the course of the mission.

And so the scientists for years were clamoring to be

allowed this opportunity to take data when we were

cruising over the rings.

And that's, in fact, what we did.

We collected a beautiful collection of images of the

highest resolution we've ever had on the rings.

And we saw many things.

I don't have the time to show you all of them.

One thing we saw a lot of was waves.

In this picture, the smallest thing you could see, the

tiniest little pixel there, is only a couple of several

hundred meters, so just several football fields, OK.

These are waves.

These are the fingerprints of orbiting moons that are

perturbing the ring particles.

You see here, something called the density wave. This is

where the perturbed non-circular orbits of the

ring particles are all phased in such a way as to give rise

to these regions of higher than average concentrations of

particles which, in fact, spiral all the

way around the planet.

These are spiral density waves.

We're looking, incidentally, on the dark side of the rings.

So what you see here as dark is actually bright, if you saw

it on the lit side.

So the highest concentration here are the dark regions.

They spiral around the planet.

These are the kissing cousins of the spiral

arms you see in galaxies.

Same mathematics was co-opted from galactic structure, the

physics of galactic structure, and applied to Saturn's rings

to, in fact, predict that when Voyager got there in the early

1980s, it would find these features.

And, in fact, it did.

With Cassini, we got just a very much better look.

These are bending waves.

These are the vertical equivalent of density waves.

This is where it's not the eccentricities of the orbits

that are perturbed, it's the inclinations.

And so this is a feature where there are crests.

This is like corrugated cardboard.

The whole ring plane is warped like corrugated cardboard, and

the crests spiral around the planet.

OK, again, these are due to the

perturbations of orbiting moons.

This was on the dark side.

When we crossed over the rings and passed on to the lit side

and then turned around and looked up at the rings as we

were receding, we saw these kinds of things.

Lower resolution picture by about a factor of three, but

still, you could see lots of waves, lots of waves.

You even see this thing, corduroy structure.

This is the perturbations of a moon orbiting, actually,

within the rings.

So lots of phenomena we got a very good look

at with these pictures.

And one thing, one remarkable and very telling discovery we

made in this collection of images, are these little

propeller features.

OK, these are the beginnings of gaps that are being made in

the rings by bigger than average particles.

They're about several kilometers across, a few

hundred meters wide.

The pixel scale here is the highest it ever got for us.

This is like a half a football field per pixel.

And so from the dimensions of these features, we can tell

the size of the bodies that are making

these incipient gaps.

And they look to be something like 20 to 60 meters in

radius, so that is a little bit bigger, several times

bigger, than the largest particle size.

OK, and this one observation has given us insight into the

particle size distribution in the rings and also will

eventually tell us something about the

way the rings evolved.

But there are even bigger bodies that are embedded

within the rings, of course, and they're having dramatic

and more obvious effects on the rings.

This is the A ring.

This is the famous F ring that is shepherded by two

shepherding satellites called Prometheus and Pandora.

This gap is called the Encke gap.

Keep this gap in mind.

This is called the Keller gap.

I'll show you this later.

This gap is about 300 kilometers wide.

It is inhabited by a moon called Pan.

These, by the way, are all those density waves that are

created by other moons orbiting Saturn.

The next picture is going to show you a high resolution

view of this that we got during the Saturn Orbit

Insertion Maneuver.

And there you see it.

It's so beautiful, it looks simulated, but it's actually a

real image.

There are ringlets in this gap.

Remember this is 300 hundred kilometers wide.

These are waves in the edges of the gap that are created by

the perturbations of Pan.

It excites eccentricities in the orbits of the

particles in the rings.

And those eccentricities, again, they're all properly

phased that they give rise to this pattern.

You can see the streamers spiraling away from this edge,

also again the perturbed and phased motions of particles.

And here is a view we got later on in

the mission of Pan.

This is the culprit.

This satellite is about 30 kilometers across.

The rings are only a few tens of meters so you can see it

protruding up and down.

It's a beautiful picture.

It was very thrilling to finally get a

closer view of Pan.

We also looked closely at the Keeler gap, which is 42

kilometers across, and we discovered Daphnis.

This is a little moon, only eight kilometers across.

It's doing the same thing on the edges of its gap.

It's raising waves.

And the study of these systems, a moon in a gap in a

disk of material--

though I should say these systems provide the best

analogs we have available to us in our solar system for the

systems that are being discovered

nowadays, every day.

That is growing planets or protoplanets in disks around

of the stars.

And the study of the manner in which these bodies, like Pan

or Daphnis, open up the gap in their disk and keep the

material at bay through their gravitational interactions is

going to prove very fruitful for the study, or for

investigations, concerning planet formation,

understanding how, for example, Jupiter, a planet

like Jupiter, growing out of the solar nebula, accreting

material little by little, getting bigger and bigger,

finally comes to get so big, it truncates its own growth by

opening up a gap.

Now one of our main objectives was also to determine the

physical characteristics of moons that were orbiting near

the rings and also the physical characteristics of

any moons that we might discover, because we were

suspecting that their physical characteristics would tell us

something about their origins.

And that's, in fact, exactly what we've done.

This work has gone on in my group in Boulder, Colorado.

And let me first pause here and tell you our general

notions about how rings come about, in case you don't know.

The common wisdom says that there was a body, very likely

a pre-existing moon in orbit around Saturn that got bashed

up by an incoming projectile.

And that material eventually spread out to form a ring.

It's just a simple, predictable, physical process.

It spreads out the former ring.

There are collisions.

The collisions are very elastic.

They grind down the particles, but they also flatten the

system into a ring, OK, a ring that, as I said, inhabits the

equator plane of the planet.

OK, another idea is that the pregenitor body that forms the

rings maybe came in from afar.

Maybe it was a body that came in from the Kuiper Belt.

But anyway, the idea is, a catastrophic destruction of a

pre-existing body, material gets swept up in and circles

the planet.

Well over the last three years, we've accumulated

enough information on the ring moons, like Pan, like Daphnis,

and also like Atlas.

This is a body orbiting outside the outer

edge of the A ring.

This is the Keeler gap.

This also is about the size of Pan, 30 kilometers across,

looks like a flying saucer.

And also, Pandora, this is bigger, 81 kilometers across.

This is one of the F Ring shepherds, OK.

We have now information on the sizes, the shapes, the orbits

of these bodies, even their masses and their densities.

And putting all this together, we have found that these

bodies are shaped like you would expect for a body formed

by accretion.

So in and of themselves, they are not the remnants of this

collision that form the rings, but we think, instead, that

they have grown around a denser core.

And that denser core may be something that dates all the

way back to the original creation of the rings.

So we're getting glimpses of the chronology of events in

the Saturn ring-moon system from Cassini so far.

And speaking of moons, Saturn is accompanied by a very large

and diverse collection of them now.

There's something like 57 moons.

There may even be more, because I only looked

about a month ago.

They are being discovered all the time.

They range in size from a few kilometers across to Titan,

which is Saturn's largest moon.

It's as big across as the US.

And it's the inner collection of moons, which go out to only

a few million kilometers from Saturn.

That is the system that's being investigated by Cassini.

And this system is of particular interest because it

is believed because these moons are all in orbit in the

same plane, they're all orbiting in the same direction

around a big massive central body, they are like a

miniature solar system.

And so our goals in studying the Saturn satellite system,

this particular component of it, were not only to come away

with accurate measures of their compositions and their

physical characteristics, not only to further our

understanding of their geological histories and their

thermal histories and so on but also to study the system

as a whole with an eye towards testing our ideas about

planetary formation, both the formation of our own planet,

and others we are discovering today.

Now the Cassini tour through the Saturn system is


It's enormous in magnitude, calls for 82 close satellite

flybys within four years.

All of them are closer than the flybys that were conducted

by Voyager.

44 of those are of Titan alone.

And the remainder of them were flybys of this handful of

medium-size moons that are, as I said, within a few million

kilometers of Saturn.

And some of these flybys were exquisitely close.

They flew as close to these moons as the Space Station

flies above the Earth.

And most of these exquisitely close flybys were conducted in

the year 2005.

I call that the Year of the Moon.

That's when we came up close and personal to all of these

and have discovered some remarkable things about their

geologies and physical characteristics.

And we certainly, if you've been paying attention, seen

that we return some fantastic images.

This is Tethys, a moon that's about 1,000 kilometers across.

That's about 600 hundred miles, sports some amazing

basins on its surface.

Here it's shown with the rings in the background, one of our

beautiful images.

This is Rhea, 50% bigger than Tethys, so

1,500 kilometers across.

That's about 1,000 miles, OK.

So we're talking about something maybe the size of

the Southwest US.

This is Rhea hiding behind the rings.

This is one of our beautiful pictures of Dione.

This is about the size of Tethys, again about 1,000

kilometers across seen against the glow of Saturn with the

rings in the foreground.

Here's another view of Dione, OK, taken at very high phase

angle as the sun was either rising or setting.

I don't remember.

And here's a close up of that.

OK, now I don't know about you but this

calls out for an astronaut.

Doesn't it?

Don't you want to see an astronaut walking across the

surface of that?

Actually you wouldn't be able to resolve an astronaut

because the smallest pixel here is about 100 meters, so

that's about a football field across.

This is actually a very big, very large crater.

And then here's our Death Star moon, Mimas, OK, two and a

half times smaller than Dione.

And then smaller again, about two times smaller than, or

half the size of Mimas, is Hyperion, looking like a great

cosmic sponge.

And then finally, I'm going to show you Iapetus.

Iapetus is a moon that's half the size of our moon.

It's about the size of Rhea, 1,500,

1,400 kilometers across.

And we have found some fantastic geology on Iapetus,

as you can see.

This is the moon that's half black on one side, half white

on the other, half black and white.

And here you can see this amazing landslide at the

bottom of a 15 kilometer high cliff.

OK, so it's not out of the question in my mind that some

day your descendants might be taking extreme excursions into

the Saturn system and ice climbing on

the cliffs of Iapetus.

And I envy them.

I should say that all of these moons are made

out of water ice.

That's the most abundant material in the Saturn system,

in the satellite system.

And water at these temperatures is a

rock-forming mineral.

So they're mostly water ice.

All you have to do is look at the cratered surface of these

bodies to know that there was a time many, many years ago,

in the early history of the solar system, when there were

a great many bodies careening around the solar system and

smashing headlong into the planets and forming satellites

at tremendous speeds.

And these collisions did a great deal to actually build

our solar system and make it look like it does today.

They were responsible for allowing the planets, first

and foremost, to grow to their present size.

It was cometesmal, small comet-like bodies that made up

Uranus and Neptune, for example.

It was a collision that was responsible for tilting Uranus

on its side.

It was a collision with a Mars-sized object that

actually created our moon.

Soon after the Earth formed, a Mars-size object came and

collided with the earth and pulverized the outer layer,

throwing it into space, from whence that material

collected, and the moon formed.

And as I showed you, collisions are responsible for

smashing up satellites and creating ring systems.

So collisions, in fact, are the creators of worlds, and

they are the destroyers of worlds.

And don't forget, it was a collision that wiped out the

dinosaurs and cleared the way for the eventual development

and evolution of the primates, of which we like to think that

humans are the culmination.

Or put it another way, it would been very hard to invent

Google with a Tyrannosaurus rex breathing down your neck.

So collisions have actually done a great deal for us.

And they have been a tremendous process of force in

sculpting the solar system.

And the craters that they create on the surfaces of

these bodies can actually be studied and examined.

Their morphologies can be examined to give us

information about the properties of the material

into which they've been placed.

And to understand something of a chronology of events in the

Saturn system.

If you look at the distribution of craters, and

you know something about the projectiles population, you

can say something about the order of events, that things

happened in the system.

I don't have the time to go through all that we are

learning about that right now, but I am going to concentrate

on two moons in particular which have stood out over the

last 1,000 days.

And they are Titan, which is Saturn's largest moon, about

50% larger than our moon.

And then Enceladus, which is a tenth the size of Titan.

Now Titan has long intrigued planetary scientists.

And before Cassini arrived there, it was the greatest

single expanse of unexplored terrain that we have left in

our solar system and was believed to be, in many

respects, more like its environment.

Surface environment was believed to be more like the

Earth's than any other that we have in the solar system.

Like the Earth's, its atmosphere is very thick, and

it consists largely of molecular nitrogen.

Like the Earth, its thermal structure consists of a

troposphere, where the temperature decreases as you

go up, And then a stratosphere, where you turn

around, and the temperature increases as

you go further up.

Like Earth's, its atmosphere has a mild greenhouse effect

near the surface.

So its surface is some twenty degrees warmer than it would

be otherwise.

But its atmosphere lacks free oxygen, and it is suffused

with small but significant amounts of methane, and

ethane, and propane, and other simple organic materials

containing hydrogen carbon, which we called hydrocarbons.

And for all these reasons, Titan's atmosphere was

believed to be an analog, or at least the closest analog we

would ever find in our solar system to the atmosphere that

scientists believe existed on the surface of the Earth prior

to the emergence of life.

And that's not all.

The compounds, the organic materials in the atmosphere

form a ubiquitous haze that is formed, by the way, from the

break up of methane high in the atmosphere, separating the

carbon and hydrogens.

The carbons join together.

They create these polymers, which end

up being haze particles.

Those haze particles, it was suspected,

would grow over time.

And they would fall over the years.

Over billions of years, they would fall, or at least as

long as Titan had an atmosphere, would fall down to

the surface and possibly coat the surface

with an organic sludge.

OK, and some of these compounds, methane and ethane

in particular, could be liquid at the surface of Titan

despite the unimaginable cold of minus 300 degrees


In fact, what water does on Earth, methane does on Titan.

It can be in the form of a solid, a liquid, or a vapor.

So all of this opened up a world, literally, of bizarre


First of all, you have hundreds of kilometers of

globe-enveloping haze, OK, surrounding Titan,

making its days dark.

High noon on Titan is as dark as deep Earth twilight is here

on the Earth.

We could have patchy methane clouds

floating above the surface.

And in places, we might have rain, gentle methane rains

falling slowly because the gravity is less than it is

here on Earth.

And these rains over time could cut gullies.

They could form deep canyons.

They could form rivers, and cataracts, and cut canyons,

and wash the sludge, perhaps, off the high mountains, and

into having the drain into low-lying basins and craters.

So stop and imagine this environment for a while.

You're standing on Titan, a moon in

the outer solar system.

You're standing on an icy surface, a water ice surface.

It's very dark.

It's broad daylight, but it's dark.

It's cold, impossibly cold.

It's misty.

And before you lies Lake Michigan

brimming with paint thinner.

That is what we thought existed under the clouds,

under the haze of Titan before Cassini got there.

So it was with tremendous anticipation that we looked

forward to Cassini's exploration of Titan.

And what we have, in fact, found on Titan, though

different in detail, is every bit as fascinating as the

story that I just described to you.

And for those of us involved in this mission, it's been

like a Jules Verne adventure come true.

Titan's atmosphere is, in fact, very thick.

You can clearly and beautifully see that in this

image that is backlit by the sun.

And you can see the rings in another moon in the background

in just one of another of our tremendously gorgeous images

that we're taking around Saturn right now.

But despite the haze and the impenetrable atmosphere, we do

have instruments on Cassini that can

see down to the surface.

We outfitted our cameras with filters that allow us to see

in the near infrared through spectral channels that

actually allow light to penetrate through the


And also, there is a radar instrument on Cassini, which

is virtually identical to the instrument that mapped the

surface of Venus with the Magellan Spacecraft in the

early 1990's.

And with all of these, we have finally been able to

reconnoiter the surface of Titan, if you will, and open

up this previously unexplored terrain to view.

And here's what we first saw of the surface of Titan from

the Cassini orbiter.

First, you can see bright, and you can see dark, OK.

And that's what it looked like to us, not

exactly easy to interpret.

For a planetary geologist to look at an image like this,

the first thing they see is something linear.

This looks linear.

This looks basically linear.

That says tectonics.

There is something there that's cracking the surface in

a linear fashion, like the San Andreas fault, OK.

We looked on the other side of Titan, This is a higher

resolution view of the same thing I just showed you.

So we see circular things.

We don't see too many circular things, OK.

Circular thing are craters, we think, maybe craters.

Maybe they're calderas, Maybe they're

volcanoes, not really sure.

This looks like a caldera.

We see things that look like they flowed.

We see what we called pull apart features, things that

looked tectonically ripped apart, but

very hard to interpret.

We do see black.

We do see white.

Then we look at the other side of Titan.

We see again bright and dark.

Even though we weren't quite sure what we were talking

about, we started to call these things islands, because

they looked like islands.

But we didn't know.

Were they regions that were higher than the surroundings?

Were they lower than the surroundings?

We had no clue.

It's always a hazy day on Titan, OK.

So there's no shadows.

Without shadows, it is very difficult to tell what's up

and what's down.

And so that left us really bereft of definitive


And there was nothing that was so unambiguous, so clearly a

feature or a pattern that we had seen on Earth that we

could say ah we understand this.

We were really at a loss to know.

But we did see, again, on this side, we saw some things that

look like craters.

And again, I said we called these things islands.

We got to calling this Great Britain.

This was Ireland.

This was France.

This was Iberia.

This was Peloponnese.

The geography is not quite right, but it

didn't bother us.

We saw things that looked like they were wind swept, OK, but

not much else we could see.

But then a remarkable event happened.

And it was one that we knew would be the Rosetta Stone and

help us interpret our images that we

were taking from orbit.

And that was about six months after getting into Saturn

orbit came what many regard as the highlight of Cassini's

explorations of Titan.

A flying saucer-shaped device, which had been carried by

Cassini for seven years, was deployed to the Titan


And successfully drifted on a piece of fabric for two and a

half hours through the hazy atmosphere and came to land on

its surface.

This was that the deployment and a mission of the Huygens

probe, the European-built Huygens probe.

And this I can tell you was a positively extraordinary


And for those of us in Darmstadt, Germany at the

European Space Operations Center, where this event was

monitored, it was a very emotional event.

It was the day that humans had landed a device of their own

making in the outer solar system.

It was like living science fiction.

And I've come to call this a grown men crying kind of day,

because grown men were disappearing into corners to

have their own little private moments during this event, so

that they wouldn't get busted by their colleagues, being

seen losing it because of the overwhelming emotion of the

whole event.

And it was, to me, an event that was so significant, it

should have been celebrated with ticker tape parades in

every city across the US and Europe, and unfortunately that

didn't happen.

But it was extraordinary for another reason.

And that's because the celebratory presentations

during this event were given in just a host of accents.

English was used, but they were given in English accents,

in American accents, in French accents, and Dutch, and

Italian, and German accents.

It was, in fact, for me, a moving demonstration of what

the words United Nations is supposed to mean.

And that is a group of nations joined in a common cause.

And in this case, it was a massive undertaking to explore

a planetary system that for all of human history had been


And now humans had touched it with something

of their own making.

It was a very remarkable and historical day, and certainly

a day that I'm not likely to forget.

I don't think anyone there will forget it.

But anyway, I digress.

The probe took many measurements of the atmosphere

on its two and a half hour descent down to the surface,

including panoramic images.

And it's hard to describe what it was like to see those first

images that were released for public consumption, because it

was a shock.

And this is what we saw, OK.

This is a mosaic, in fact, of images that were taken as the

probe descended.

And we saw this region here, OK.

And it was shockingly easy to interpret.

It was, as you can see, drainage pattern that could

only be produced by a flowing liquid.

In fact, you can follow the channels in this drainage

pattern, and they actually move away from this boundary,

and go down here, and join this tributary.

And they all drain into this region right here.

OK, we know from stereo images taken during this descent,

you're looking at something here that's high.

This is about a hundred meters higher than this area.

The next picture is just-- this by the way is taken at

1600 kilometers up.

This picture is taken it eight kilometers up, OK.

You're looking at a shoreline, OK, we weren't sure, at this

point, was this liquid, OK.

But you're looking at something that looks like a

shoreline, OK, and islands, offshore islands.

OK, bear in mind, 16 kilometers, 8 kilometers,

that's roughly airliner altitude.

If you were going to take to get in an airplane and fly

from San Francisco to New York, you would be flying at

something like 12, 11 or 12 kilometers altitude.

OK, so this is the view you would have out the window of

Titanian Airlines as you flew across the surface of Titan.

And maybe, someday, someone will actually get the chance

to do that.

And then here, finally, is the picture that we collected on

the surface, the Huygens probe took once it landed.

OK, you can see the horizon in the background.

You could see boulders in the front.

But they look big.

But they're actually no bigger than about

6, 12 inches across.

So they're like stones, almost certainly made

out of water ice.

These are, again, stones or pebbles.

They look very well sorted.

The idea is that probably some liquid flowed across this

surface at one time and sorted all these stones and pebbles.

But the probe landed not in liquid.

It landed in what is the equivalent of a Titan mudflat,

an unconsolidated ground that is suffused with liquid

methane and very likely made of the accumulation of the

organic matter that I told you falls out of the sky and

probably accumulated in low lying depressions on the

surface, very much like what had been expected.

So all told, the Huygens Mission was a glorious success

and a triumph and gave us the kind of ground truth that

helped us, and is helping us still, interpret our images

from orbit.

But still at this point, this was early 2005, there were no

open bodies of liquid.

We thought we'd find lots of liquid on the surface.

No open bodies of liquid to be seen anywhere, not from

Huygens and not from the orbiter.

And still, of course, the exploration of Titan continued

from orbit.

We continued to take pictures.

And the radar instrument continued to take its data.

And it discovered another unambiguous pattern in the

equatorial region of Titan.

It discovered that vast regions were

covered with dunes.

These dunes are 100 meters high.

They're several kilometers across.

They go on for hundreds and hundreds of miles.

There's a region that fifteen hundred kilometers worth of

surface areas extent around the equator is covered with

these dunes.

OK, this is an enormous geological feature on the

surface of Titan.

And it indicates steady bi-directional flow of wind,

or else you wouldn't get dunes like this.

And obviously conditions that are dry

enough to loft particles.

That's how you create dunes, so not only no bodies of

liquid, very dry conditions.

So a great puzzle, we didn't see any liquid.

We're still looking for it.

Finally, Cassini got to investigate the polar regions.

This picture was taken of the south polar region.

That's what this cross is here.

And this was the closest we got at this point to something

that looked like a lake, OK.

It has a shoreline that looks like it could be a lake, a

very dark material inside.

OK, if you fly over Minnesota and look down at the lakes,

they look black, OK.

So we thought this was probably the closest we'd come

to a lake feature.

We thought this region here was dotted, maybe, with lakes.

This was like a lake district.

Actually this is, in absolute size, the

size of Lake Victoria.

But if you scale it, relative to the surface area of Titan,

which is much smaller, it's more like the size of the

Black Sea on the Earth.

OK, so this is what we saw in the south polar region, but we

didn't have any definitive evidence that this was liquid.

It could easily have been argued this is just a residue.

Maybe there was liquid there at one point.

It evaporated.

This is the residue that's left behind.

We didn't have any definitive evidence.

And then we looked in the north polar region just this

past February.

And this is what we saw.

This is our imaging data.

And you could see these regions.

This is a cloud feature.

You could see these dark areas here.

OK, they look, again, like features we saw in the south.

One of them is very large.

In fact, if you scale it as large as the

Mediterranean Sea--

and then the radar got images that overlap, and they are

interpreting these dark areas to be liquid because they're

the darkest things that they see with the radar data.

So you are looking here at where it appears the liquids

have gone on Titan.

These are hydrocarbons, we think.

You could see some of these shorelines look like

the coast of Maine.

And not only do we see big areas, lots of big bodies, but

we see also a region that has smaller features in it that

look like the lake district that we saw in the south.

And here we're cruising over the radar data here.

And this is the pole.

So it appears that the liquid on Titan, at least during the

present season, which is southern summer, northern

winter, have migrated to the poles.

And why that should be the case, we don't know, probably

says something significant though about the

meteorology of Titan.

But all told, we have found on Titan, I think you would

agree, a very remarkable and even mystical place, one that

is exotic and alien, but also strangely Earth-like in its

geological formations and processes, and just a

fascinating place whose geologic diversity, and

complexity, and richness is rivaled by no other body in

the solar system except the Earth itself.

And we will see more of Titan in the next 1,000 days of the

Cassini mission.

But now in this tale of two moons that I'm telling you, we

move on to Enceladus.

And Enceladus is very much smaller, a tenth the size of

Titan, very bright very white, in fact the brightest, whitest

object we have in our solar system.

It's no bigger than England, or Great Britain.

And I don't mean this to be a threat, just for size


But despite its size, what we have found on Enceladus with

Cassini has completely thrown us for a loop.

First, from a close examination of its surface,

and I'm going to show you a picture now where the

resolution is ten times better than it is here.

We can see a surface that doesn't look at all like the

heavily cratered surfaces of the other moons.

This is a body that has obviously been geologically

active in the past. It is crisscrossed by tectonic

fractures at wild angles.

Many generations of cracks, and troughs, and ridges, and

so on, very deep chasms, mountain folds, and so on, a

few craters here and there but otherwise a very young, very

geologically active place.

And the mother lode of all the discoveries that we have made

on Enceladus, far and away, were found at the south pole.

And you're looking here, this is the

south pole of Enceladus.

It is circumscribed by these mountain folds and

characterized or crossed by these very deep fractures.

They're about a 135 kilometers across, just a

few kilometers wide.

This whole region is youthful.

There's no craters, obviously does have tectonic features

and folds in it.

It is characterized by elevated temperatures.

This whole region is warmer than the rest of Enceladus.

That would be as bizarre as finding that the whole of the

Antarctic is warmer than the Tropics.

I don't mean the atmosphere.

I'm talking about the surface.

The fractures here are different in color, because

they're different in composition.

They are coated with simple organic materials.

And then more surprising than all of that is what we saw

when we found ourselves in a geometry to look back in the

direction of the sun.

It's what we call a high phase geometry.

It's a geometry that highlights the presence of

very, very fine particles.

OK, and this is what we saw.

We saw that the surface from the south pole of Enceladus,

and the south pole is right here, is emerging these jets

of very fine particles extending tens of kilometers

into space and feeding--

if you take a picture like this and you process the faint

light levels with color to bring out the contours, the

faint light levels, this is what you see.

These jets are feeding a huge plume that extends--

in fact, we see in other pictures-- extends tens of

thousands of kilometers away from Enceladus.

So this, in fact, was quite a surprise.

It turns out we know now that these jets of particles are

accompanied by water vapor, and water vapor that is laced

with simple organic materials.

OK, the analysis of all this information, other pictures

we've taken of the jets of Enceladus, including the

information gathered by other instruments about the water

composition and the composition of the organics,

all of this, was put together by my team and I. And we have

reached, I wouldn't call it necessarily a conclusion, but

we think it is possible that these jets are erupting from

sub-surface reservoirs of liquid water.

OK, and if we are correct about this, then we have

stumbled upon what I call the Holy Grail of modern day

planetary exploration.

That is we found an environment that contains

liquid water, organic materials, and excess warmth.

Or, in other words, an environment that is conducive,

possibly conducive, to the presence of living organisms.

And I don't think I need to tell you what the discovery of

living organisms or life in our solar system, should that

ever happened, the kind of implications that would have.

Because if we could demonstrate that life had

arisen not once, but twice, independently in our solar

system, then we can infer that it has occurred a staggering

number of times throughout the 13.7 billion year history of

the universe.

Cassini, of course, continues to orbit Saturn.

It obeys our every command.

It's returning magnificent image after beautiful image of

a planetary system that I think, you would agree now, is

rich in beauty and otherworldly phenomena.

And I don't think I have to convince the inventors of

Google Earth of the value of images of planetary bodies,

and of the culture-shifting power of images.

Our space program has led the world in taking such images,

and images that have become cultural icons.

And I'm going to remind you of a couple of them.

Those of you who were alert and coherent during the 1960s,

I don't know if any of you were even alive during the

1960s, I was.

You'll remember this famous picture taken by the Apollo 8

astronauts on December 29, 1968.

And this was a picture that had an enormous impact on

earthlings and on our perspective of our cosmic

place and our responsibility for

stewardship of our own planet.

I think it's even credited with adding impetus to the

environmental movement during the '60s.

Well, eight months ago, we on Cassini, I'm very proud to

say, caught sight of something again that no human had ever

seen before.

It was a total eclipse of the sun seen from the

other side of Saturn.

OK, and you can see in this gorgeous image, the main rings

highlighted backlit by the sun.

You can see the refracted image of the sun.

This is the light being bent around Saturn by the


You can see the whole system is encircled in this beautiful

blue ring, which is coincident with the orbit of Enceladus.

This is a ring that is the result of

exhalations of Enceladus.

And if you look closely enough, and as if this weren't

brilliant enough, within this impossibly lovely scene, you

can spot from a billion miles across interplanetary space,

our own planet Earth cradled in the arms of Saturn's rings.

And I think it will be a long time before we see anything so

moving again.

I believe that nothing has greater power to alter and

correct our own impression of ourselves, and where we fit

into the scheme of things, than seeing ourselves from

afar and capturing a glimpse of our own little blue ocean

planet in the skies of other worlds.

And that changing mindset, that changing worldview, may

in the end be the greatest legacy of all our

interplanetary travels and the finest reward that we'll ever

receive for this, hopefully, never-ending journey of

discovery that was begun 50 years ago.

Thank you.

Leslie, what do we do now?

Do I take questions?

OK, questions, are there any questions?

Can we put the lights up, please?


AUDIENCE: Where is the methane on Titan coming from?

DR. CAROLYN PORCO: Well, that's a good question.

That's a 64 million dollar question.

People are working hard to try to figure that out.

It could be outgassing.

That's the explanation du jour is that it's being outcast

from the interior in volcanic eruptions perhaps, or somehow.

And then, of course, there are those who like to think that

it's bacteria on the surface of Titan that can live there

and produce methane.

That's another maybe not so popular view, but there are

holdouts for that point of view.

Any other questions?


AUDIENCE: Is there any way we can find these pictures?

DR. CAROLYN PORCO: Yes,, it stands for

Cassini Imaging Central Laboratory for Operations,


That's where we post all the images that we

take with our cameras.


AUDIENCE: On this picture, can you explain the image?

Why doesn't the ring connect?

Why is there discontinuity there?

DR. CAROLYN PORCO: Do you mean this?


DR. CAROLYN PORCO: OK, first, you have to know that this

picture was taken--

I forget now myself--

it's either taken over nine hours or taken over six or

three hours.

So the spacecraft was in slightly different positions

when it was taking--

and it's a mosaic.

It's not one picture.

Lots of pictures have gone into this.

So when it was taking this picture here, it was in a

different position than when it was taking

that picture there.

So that's why it kind of looks funny there.

But you're looking at light.

You're above the rings.

The sun is below.

So you're actually looking at the dark side of the rings but

the sunlight is filtering through the rings.

And you can see, in fact, where the rings are--

well before I get into that.

This, from here down, is the southern hemisphere of the

dark side of Saturn.

And that looks bright because the light is hitting the rings

and shining back on to the southern part of the planet.

OK, and then against that bright southern hemisphere,

even though it's on the night side of Saturn, you are seeing

the silhouettes of the rings here.

So really the rings here are not lit at all.

There's no sunlight here at all.

But this is a silhouette.

So you wouldn't see anything ring-like at all were it not

for the fact that you're seeing a silhouette.

OK, and then because the rings orbit in exactly one plane,

that plane intersects the planet right there.

So no light is getting there.

AUDIENCE: So is this [UNINTELLIGIBLE] right on the

edge of the planet?


AUDIENCE: Yeah, all along the edge of the planet, the rings

don't connect up, that's because--

DR. CAROLYN PORCO: That's the shadow.

AUDIENCE: That's the shadow versus the actual rings?

DR. CAROLYN PORCO: That's the shadow, the shadow of Saturn

cast on the rings.



AUDIENCE: Why are the rings of Saturn [UNINTELLIGIBLE] any

other gaseous planets?

DR. CAROLYN PORCO: It could be just a matter of statistics.

Right now, we see the solar system when Saturn happens to

be the planet that has big rings around it.

If estimates of the age of the rings, and this is also being

debated among Cassini scientists right now, but

going in to Cassini, our estimates were that rings

didn't live longer and weren't older than about a few hundred

million years old.

So to just calibrate that.

Back in the days of the dinosaurs,

Saturn had no rings.

OK, we just happen to be seeing it now when a

catastrophic disruption of a pre-existing body, or maybe a

capture of a body happened, it got broken apart

and it formed rings.

There are moons around Neptune that exist, within what we

call the Roche limit.

That is they're close enough to Neptune that if they get

broken up tomorrow, if all of the moons within that region

got broken up tomorrow, they would make a ring that was

comparable to, at least, the A ring of Saturn.

So it just might be timing, when we

happen to be here observing.

If it's true that rings are just continually created,

eroded, created, and eroded.


AUDIENCE: What's the expected lifetime of the Cassini


DR. CAROLYN PORCO: The Cassini what?

AUDIENCE: Imaging, how long is it going to last?

Will it run out of power, or fuel or navigation, or--

DR. CAROLYN PORCO: OK, so the real

limit, you know is politics.

It's how much money the American Congress wants to

give us to continue going, literally.

The spacecraft is in good health.

It's stabilized on gyros, and there were four of them.

One of them was redundant.

And I think one of the remaining three has arthritis,

a little bit of arthritis.

But even if the gyros went, there's still thrusters.

We could turn the spacecraft with thrusters.

In that case, we're using fuel.

But that could still be done.

So we could still turn hither and thither and take pictures.

Fuel is a precious commodity.

We're planning the extended mission now, so we'll almost

certainly go through 2010.

And then after that, we'll plan through 2012.

Almost certainly by then, our budgets will be way down.

There's nothing on the horizon that looks like it's going to

limit us mechanically, electrically, functionally.

It's just how long they'll provide funding for it to go.

You know, these missions have a nasty habit of not dying.

They can't even kill the Mars Rovers.

I think they've tried to drive them off cliffs.

They won't die.


AUDIENCE: Two questions, do you have to pan the camera for

most of the images because the light levels are low?

Or [UNINTELLIGIBLE] exposure times can be short enough not

to turn the spacecraft?

DR. CAROLYN PORCO: Oh, I see what you're saying.

OK, let's do one question at a time, because by the time you

ask me the next one, I'll forget the first. We do pan

but not really because light levels are low.

Generally, we do that when we're flying so close to a

body that the relative motion would give us smear if we

didn't do that.

So Cassini is an amazing spacecraft.

It's been programmed so that we could say to it, point to

this latitude and longitude on this satellite.

And keep the bore side pointed there.

And it knows that as the thing is turning, it does this.

OK, but for light levels, all we have to do, it's like a

camera on Earth.

All we do is keep the shutter open longer.

And because the spacecraft is so massive,

it's enormously stable.

So we point it, and it just stays there.

And we can keep the shutters opened for minutes and get

beautiful images.

We could never do that on Voyager.

On Voyager, we couldn't expose longer than a few seconds

without getting smear.

So it's a tremendous improvement.

That's one of the reasons why our pictures look a lot better

than Voyager pictures.

The other is that were using a CCD instead of a

selenium-sulfur vidicon tube, which is what the Voyager

cameras were.

What's your second question?

AUDIENCE: The second question is what's the data rate back

to Earth, and do you have to buffer the images on the


DR. CAROLYN PORCO: Oh yeah, we have to buffer.

And I don't remember the data rate.

Isn't that ridiculous?

But I don't remember.

I don't even want to say because I'll guess, and I'll

get it wrong.

And this is being filmed.

And it'll go out there, and I'll forever be wrong.

So I won't say it.


AUDIENCE: Are there any return trips

planned to Titan's surface?

DR. CAROLYN PORCO: Oh there's lots of discussion right now

about what the next missions are going to be.

And there's even a debate, because missions are very hard

to get, especially missions of the type that we are

conducting now.

All the simple things have been done.

So missions now are much more complex.

They have to carry many more instruments.

OK, we want more data rate.

We want everything, more, more, more, because we want to

just do a better job the next time we go out.

And it takes a long time to get out to

the outer solar system.

So you don't want to do it piecemeal.

You want to send a nice, healthy, well-equipped vehicle

out there to do what you want it to do.

So the big missions are few and far between.

And there's always debates about what we should do next.

So there's a debate going on right now.

Should the next big mission be to the Jovian moon, Europa,

OK, which is believed to have a subsurface ocean, but an

ocean that has something like ten kilometers worth

of ice around it.

Or, with the results of Cassini now have brought the

whole Saturn system to the fore as an exciting place, and

an important scientific place to go, I should say, in a

place that's scientifically important to return

to because of Titan.

And also because of Enceladus.

If we're correct, and I have to say that's a big if, we

still need to investigate this, and it needs to be

looked at with a lot more detail.

If we're correct that the jets are erupting from liquid

water, then Enceladus has just jumped to the front of the

line in my opinion.

There's a body of astrobiological interest in

our solar system.

I'm fond of saying this.

All you have to do is land on the surface, look up, and

stick your tongue out.

And you've got what you came for.

And you know wouldn't it be amazing if there were microbes

in those ice particles, OK, flash frozen.

So that would be an exciting place to go to too.

But there's the people who want to go to Europa.

Then there's those of us who think we should be going back

to Enceladus.

And then there's the people who think well let's go back

to the Saturn system, but we really should

concentrate on Titan.

So there's just a lot of debate going on right now.


AUDIENCE: Is there anybody who wants a manned mission?

There's so much good science being done by unmanned stuff.

Why is there this push to send someone to Mars?

DR. CAROLYN PORCO: Well, OK, so I'm a person who obviously

is deeply involved in the robotic side of things.

And I'm in favor of sending humans back into space.

I don't know if you read my editorial that I wrote in the

New York Times, where I basically pointed out

something we've all known.

People have been afraid to say it.

But I think it's being said more and more that the

previous 25 years of the human flight program has been a

waste, because we've done nothing but go around and

round in circles.

OK, we abandoned the Apollo program.

We abandoned the Saturn V, which was the biggest, most

powerful vehicle the US had ever built.

We could have used it.

We could have been way ahead of where we are now in the

human exploration of the solar system had we not done that.

And it did not cost less to go with the shuttle.

It cost more in the end.

But there has been always this friction between the human

side and the robotics side.

And I'm hoping that maybe soon, the twain shall meet.

And even the fans of the robotic exploration will see

the benefit of having, at the very least, developing

vehicles that would be powerful enough to send humans

to the moon and Mars.

We could also use those same launch vehicles to go out to

visit a planetary system like Saturn.

We could do very much more if we had those vehicles.

I just told you that the tortured path we had to take

to get Cassini, six metric tons, to

get Cassini to Saturn.

OK, if we were going to take a path like that but had a much

larger launch vehicle, we could have carried much more

than Cassini.

We could have carried a Cassini orbiter.

We could have carried up a vehicle was on the orbiter, a

vehicle that could have landed on the surface of Enceladus,

and a balloon that we could have deployed to Titan to

basically get blown around by the winds on Titan and

investigate the surface that way.

We could have done so much more.

So I would rather not there be this tension, this conflict

between the two.

I think that I could go on and on about this topic, OK.

The NASA budget is 16, 17 billion dollars.

That's 0.6%, 0.5% percent of the amount of money that the

federal government spends.

OK, that's a minute amount of money for the

whole entire agency.

OK, you could double the NASA budget, and it would go

unnoticed, OK, except for those agencies that happen to

be in direct conflict when it comes down to budget


But put all that aside.

You could double the NASA budget.

It's a tiny agency.

It's a tiny budget.

We are a wealthy country.

We could do both.


AUDIENCE: How hard would it be to send a spaceship out there

to bring [UNINTELLIGIBLE] back?

DR. CAROLYN PORCO: It would be difficult because--

you're talking Titan or Enceladus?

It matters because Enceladus is closer to Saturn.

It's deeper in the gravitational well.

Once you get into the gravitational well, and that

takes energy.

I described to you what we had to do.

We had to slow the spacecraft down.

You actually have to expend energy to slow down.

Once you get into the gravitational well, then you

got to get out.

OK, so it's difficult to do that.

That would not be the very next thing we do.

The very next thing we would do is send capable enough

instrumentation there to make the kinds of measurements we

think we need to make.

If you're talking about Enceladus, we'd want to

investigate the properties of the organic materials, what's

called the handedness of it to see if it's organics that has

had any biological processing done to it,

that kind of thing.


AUDIENCE: I was very depressed to see that the New Horizons

spacecraft was just a flyby.


AUDIENCE: And those of us who were alive with the first Mars

flybys where we looked and said uh, nothing there, looks

like the moon.

Realize flybys are very misleading and frustrating,

especially with [UNINTELLIGIBLE].

So what were the arguments pro and con for that?

DR. CAROLYN PORCO: Do it now or we're going to be dead by

the time it ever happens.

That's the somewhat of a joke.

But there's something to be said for flybys because you do

have to reconnoiter the place you're going to even know what

kind of instrumentation you want to send there next.

So it wasn't a foolish thing to do.

It would have been nice but it wasn't a foolish

thing to do to flyby.

It would be a foolish thing to do now to send flybys to

Uranus and Neptune, for example, because we've

already done that.

The next missions to Uranus and Neptune, in my opinion,

need to be orbiters.

Yet there are some people who are saying well, we're never

going to get enough money for orbiters.

Let's do more flybys.

You see, this is the bane of living with limited resources.

AUDIENCE: Is it even technologically possible to


DR. CAROLYN PORCO: It's difficult, actually.

When you say, it's difficult just to get out there and--

AUDIENCE: Is it possible?

DR. CAROLYN PORCO: It would be possible if you had enough

resources, yeah.

Why do you say that?

AUDIENCE: How big of a rocket would you need to send it?

DR. CAROLYN PORCO: Well, yeah, you need a big rocket to carry

a lot of fuel and so on.

We don't have the capability now to do it.

I didn't know if that's what you were saying.

You don't really mean is it possible.

You mean is it practical.

Is it presently practical?



AUDIENCE: So there's something I never understood about NASA,

and I continue to not really understand.

DR. CAROLYN PORCO: I probably don't either.

They don't have heated toilet seats.

AUDIENCE: Oh, yeah, that's a problem.

So I noticed that most of these missions are extremely,

for obvious reasons, frontloaded in time, and

resources, and research.

And then basically, at the end of the day, we

bet it all on one.

And if we're really lucky, two spacecraft--

whereas the actual assembly cost and part cost of the

spacecraft is probably a small part, or in this case, probe,

is a small part of the entire research budget.

So why not launch ten probes and if five of them break,

then whatever.

At least we don't have these incidents like we're trying to

approach Mars after a ten-year project and all of a sudden,

English and metric units get messed up, and oh well, there

goes 10 years and 58 billion dollars.

DR. CAROLYN PORCO: OK, I think you're under the wrong

impression that the costs of the vehicles, the cost of

building the vehicles, the instrumentation, the cost of

building all the software and so on, that is used to operate

the spacecraft, and the instruments is way more than

we have for research.

That is the vast bulk.

For the scientists involved, this is always a tremendous


We have budgets that allow us to take pictures, archive

them, put them in the planetary data system archive,

and very little money to actually do research.

So that's where all the money goes.

AUDIENCE: Sorry, by research, I meant the whole R&D and

engineering effort of actually designing a spacecraft in the

first place, so that the idea would be-- and maybe I'm

totally wrong here-- but it just seems that the cost of

the physical craft, once you've done all the

engineering work and all the software design is essentially

very small compared the entire project.

So why not launch ten probes instead of one?

DR. CAROLYN PORCO: Well I think you may

be wrong about that.

But that's a philosophy that had been followed in the early

days of NASA.

There was always redundant spacecraft because they always

expected one to go belly up.

But we don't do that anymore because the spacecraft are

getting more and more complex.

And there is some recurring cost for building a second, a

third, a fourth, and besides you gotta operate those too.

It's expensive in people time and that's really where all

the funding is, so.


AUDIENCE: Just to follow up on that question,


what could be the additional cost [UNINTELLIGIBLE]

first craft to launch another craft of exactly the same

thing with say, just one line of code changed?


I don't know the answer.

I don't know the exact number.


AUDIENCE: That's right but--

DR. CAROLYN PORCO: I didn't hear what you-- you said it's

really a what job?

AUDIENCE: It's a custom job?

DR. CAROLYN PORCO: Custom job, yeah, that's right.

AUDIENCE: [UNINTELLIGIBLE] target to target.

DR. CAROLYN PORCO: Well, OK, so there were good intentions.

The Cassini spacecraft was supposed to be--

there was a mission called CRAF, comet rendezvous

asteroid flyby.

The CRAF Mission the Cassini Mission was supposed to be

identical spacecraft.

It was called the Mariner Mark II spacecraft line.

They were going to build lots of these vehicles.

Design them and then just send one to Saturn, one to a comet,

one here, and one there.

And then as always happens, budgets get cut, and so you're

back just building one.

In fact, a CRAF Mission got canceled.

So it's a good concept, but I think it's just because things

are getting more and more complex, it ends up being

custom because you only have the budget for one.

Any other questions?

OK, well thank you for staying so long.

The Description of The First 1000 Days: Cassini Explores The Saturn System