The First 1000 Days: Cassini Explores The Saturn System

Uploaded by Google on 25.07.2007


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.