RAW TRANSCRIPT -- NOT YET REVIEWED FOR CORRECTIONS BY CASSINI PERSONNEL

**FTS-NASA-VOICE**

**Moderator: Ms. Trina Ray**

**July 29, 2008**

**1:00 pm CT**

Amanda Hendrix: Okay. Thank you. So hi everybody. Welcome to the Fourth
Anniversary CHARM Telecom. This is Part 2. Last week we had the first
part and now we are on the second part. There's so much information to
cover that we have to break it up. And today we're going to be hearing
about magnetospheric science and about Titan science.

And so we have with us Doctor Claudia Alexander, who is the Cassini
project staff scientist and is a well known magnetospheric scientist.
And she's been involved in the Galilean mission and also she is the
project scientist on the Rosetta mission. So we're pleased to have her
with us today.

And we also have Doctor Elizabeth Turtle, who we're also very pleased to
have with us. We actually are lucky enough to have her two months in a
row, because she was great enough to do both the Icy Satellites last
month and Titan this month. She's at the Applied Physics Lab in Maryland
and is a team associate on the Cassini imaging team.

So welcome to both of you. Thanks for speaking with us today. And thanks
to everybody for joining us. And I'm Amanda Hendrix from JPL hosting it
here. And I think that we're going to start with Claudia talking about
magnetospheric results from the Cassini mission so far. So Claudia, why
don't you take it away?

Claudia Alexander: All righty then. So where we are right now is
physically I'm in London just so you know. If you can imagine sitting
here in the late afternoon, there's no spot of tea handy but we'll be
having that later.

And where we are metaphorically speaking in terms of with the Cassini
mission is we have just concluded the prime mission and getting ready
for the extended - go off and go for another two years on the extended
mission. And so it's a time to reflect on, you know, what have we
learned? How far did we get in our objectives? And what do we have still
to go?

So I'm going to actually walk you through what was presented to the
project by the magnetospheric working group in terms of what we started
out thinking that we were going to learn and then what we actually have
learned. And so there are some buzz words or some things that I may or
may not have time to actually address as we walk through this.

And so what I've done is I have a little appendix at the back with some
pictures that show a little bit about the different regions of the
magnetosphere just for your reference. And I hopefully will have put
those - moved them into the body of the talk so I can address certain
things. But I'll stop periodically to ask for questions and certainly if
there's a buzz word that I use that you find to be unfamiliar, don't be
shy about asking me what it means.

So the very first thing that we wanted to learn about Saturn's
magnetospheric environment was about the magnetosphere itself, to
actually - this is a region of space that's pretty much invisible to the
naked eye. And what we need to do is to use our tactile senses to really
understand what it is. So things that - instruments that sort of feel
and that detect electric and magnetic fields and these are things that
we can't see.

And so we're using the data to try to reconstruct in our minds what this
magnetosphere region looks like. And we fully expected that it would
look different from other planets. But the question is was it more
Earth-like? Is it more like Jupiter? Since it's a giant planet, you
might expect that Saturn's magnetosphere's behavior might be more like
Jupiter.

But Jupiter is a pretty unique planet in the solar system. It's got this
enormous magnetic field, very powerful, enormously large structure in
space that the whole sun would fit inside. And Saturn's magnetosphere
is, well we didn't know. So we said the most important thing is to sort
of discover what the magnetosphere kind of looks like but not looking
but feeling our way around.

So that means measuring the magnetic field, which is a vector so you
have to measure all three of its positions, angles. And then we expect
those to change with time because a magnetosphere is kind of like a
water balloon. So it's kind of always changing and so forth. And so
we're kind of not only measuring the magnetic field but how it floats
around in time.

And then we needed to measure the charged particles. And when you're
measuring charged particles, you're looking at the energy that they have
and what they're composed of and sort of how they're spiraling. They
have a tendency to spiral around in the magnetic field.

And so we're looking at what is their angular distribution at any given
time. And then we also measure the plasma waves in the environment. That
tells us a lot about the motions of plasma back and forth in the
different regions of the magnetosphere.

So after four years of going around in the magnetosphere, what did we
learn? Well we learned \-- I'm going to sort of go out of order
according to the list here on Page 3. I'm going to say that first of all
we learned that there's a brand new radiation belt.

And it's maybe technically not a radiation belt. But there's a brand new
region inside of the D ring that is related to the magnetosphere. So
when we put together all the different regions of the magnetosphere,
we're going to include a new one.

We learned that, as I mentioned in my introduction that we weren't sure
whether Jupiter was - whether Saturn was more like Jupiter or more like
the Earth. And one of the things that tells us about that is solar wind
control, whether the magnetosphere is responsive to the sun or not. And
we learned that in fact solar wind has very little effect on the -
Saturn's magnetosphere which makes it more like Jupiter.

So let me go to Page 4 and just talk about this a little bit. So on Page
4 I have sort of a rigid, you know, back when you were in school you had
a dipole magnet and you did the little iron filings and it made the
little dipolar shape.

And so when you think of a planet with a magnetosphere, you have a
tendency first to think well, you know, if you had those iron filings
they'd make that sort of dipolar shape. And then we sort of mapped out
the shape of the global magnetosphere and it's much more - I mean it's
not dipolar in shape by any stretch of the imagination.

So let's go on to Page 5. So not only do we have this sort of
spider-like/spider web-like field line stretching both on the day side
and on the night side of Saturn's magnetosphere but we have the
penetration of the solar wind, which on Page 5 is illustrated with the
little orange lines that sort of are perfectly parallel before they get
to the bow shock.

And then as soon as they enter the bow shock which is sort of the
influence of the magnetic region of Saturn, they are deflected and they
start to go around. And so at Earth the interaction of the solar wind
and the plasma that is deflected around that ends up getting into the
magnetosphere, there's a very powerful - what's the word I'm looking
for - there's a circulation pattern that is driven by the sun on Earth.

And when we look at this Figure 5, we were trying to figure out whether
the sun would have as much influence at Saturn. And the truth is that it
does not. So the next - on Figure 6, I have in the middle magnetosphere
these two orange blobs.

And basically this is where the plasma resides once it sort of - once
plasma comes in from the solar wind and also plasma coming off of the
rings and moons gets - resides in this sort of middle area in the plasma
sheet. And so we spent a lot of time measuring the energies and
directions of motion of plasma going around in that region.

I'm going to skip Slide 7. I'm not sure why I put the magnetotail in
there. But we will get to the magnetotail a little bit later in this
presentation. So just keep that in mind that on this diagram the sun is
to the left. And the magnetotail stretches out in an anti-sunward
direction.

Amanda Hendrix: Can I ask you a quick question?

Claudia Alexander: Yes.

Amanda Hendrix: Can you hear me okay?

Claudia Alexander. Yes.

Amanda Hendrix: Back to Slide 6 where you\...

Claudia Alexander: Okay.

Amanda Hendrix: So the orange regions were all the plasma areas.

Claudia Alexander: Yes.

Amanda Hendrix: Am I looking at that right, that that's end Z? It's in
like the vertical direction with respect to the equator that things sort
of start moving out after some distance out?

Claudia Alexander: So we're basically looking along the equatorial
plane. And the poles are perpendicular. So the poles would be headed
towards the, you know, the slide header and down to the bottom part. And
so\...

Amanda Hendrix: (So that) spreads out in the vertical direction?

Claudia Alexander: It does. Right. Right - in a sort of a disk form.
Okay? Yes. So there's the current sheet. And then there's the - and then
it expands into - it fills up the whole thing.

Amanda Hendrix: Are you going to talk more about that?

Claudia Alexander: I was not. But as we go along I will think of more to
say.

Amanda Hendrix: Okay.

Claudia Alexander: We'll look at the MIMI pictures. And I'll talk a
little bit more about that. Okay. So let's go on to Slide 7. On mine I'm
not seeing the number. But Slide 7 is this lovely schematic, okay, which
is kind of the picture that we put together after feeling our way around
for four years.

And now it's rotated the other way so the sun is to the right. And the
solar wind is flowing along and impinging on the bow shock and the nose
of the magnetosphere. And what we see is that it's tilted, okay?

So we learn - one of the most important things we learned about the
magnetosphere of Saturn is that it's got an obliquity with respect to
the solar ecliptic plane that plays an important role in some of the
signals that it's capable of making and where the plasma goes. So this
sort of tilted look that is depicted here is an important consequence,
one of the things that we learned and gained out of the Cassini mission.

Let's see. I'm going to make a note here that on the left of this
diagram is what we call an X line. And you'll see that there's this sort
of dolphin sort of bottlenose dolphin shape that's about, I don't know,
an inch before the end of the page. And then it pinches off. And then
there's a little red - a little bit more red stuff to the lefter of
that. Lefter is not a word of course, but more lefter - to the left of
the diagram.

So you can draw a little X where that pinch is. And the X is an
important thing that we still want to look at. Because one of the things
that we know when the Earth - when the sun is driving a magnetosphere,
we have reconnection, what they call reconnection in the tail, in the
magnetotail.

And you have plasma (sinks down), pinches things off and then that more
or less (unintelligible) reason would go shooting off down the tail
under certain circumstances. And that would be called a plasmoid. And
that's a way that plasma leaves the magnetosphere.

And so we're still searching around for evidence of what they call the
process of reconnection, which would be an important clue whether the
sun is really playing an important role at Saturn or not and we're still
looking at that.

So let me go back to Page 3 quickly to remind myself what I was supposed
to be talking about. Okay. So imaging of a rotating and dynamic ring
current is one of the findings that we got. And what I want to do is
talk about what is a ring current at Earth and what the actual images
showed us and what is still to go?

So we have on Page \-- whatever page this is, probably Page 8. This is
the Earth. And what I want to show on the right is what's called the
plasmasphere. Okay. At Earth we don't have these big disks. But we do
have a sort of balloon shaped plasmasphere, where plasma from the Earth
and from the magnetosphere gets trapped very close to the Earth right
sort of right next to the Earth's atmosphere.

As you keep going up into space you're going to be into the
plasmasphere. And on the bottom left is an image of the plasmasphere
taken from spacecraft near the Earth. And I sort of drew a picture to
the shadow of Earth's shadow. And then off to the left is where those
particles are located in the plasmasphere.

So let's go to the next page, which is - it says, "From the image
spacecraft, plasma injection at the Earth." So what happens I talked to
you just a couple pages ago about how we have this X plane and that
plasma goes shooting off down the magnetotail.

And then what also happens is the plasma comes shooting towards the
planet. And this is in a solar driven magnetosphere. And so on Earth
that process we have what's called the ring current. And in this diagram
on Panel 1 you have the normal plasmasphere.

You have the Earth in the middle there. The sun is to the right. And the
shadow of the Earth you can see. And then the plasmasphere is the green
stuff. And then the ring current as plasma comes in from the tail, you
have the brightening of the ring current which is in blue.

And then gradually that plasma is ingested into the plasmasphere. And
what ends up happening is that you generate aurora. That's the sort of
final process of taking all this plasma in.

And the next page, Page 11, shows the same kind of thing being observed
by MIMI, which is one of the instruments of the Cassini magnetosphere
suite of instruments that is in Saturn's magnetosphere imaging this
plasma injection ring current brightening as plasma is brought forward
from the tail.

And so this is evidence of not only solar control but also the process
eventually of how plasma is moving around the magnetosphere from one
region to the other - the plasma dynamics through the magnetosphere.

And I'm going to skip this next slide because one of the things we also
noticed, a very important thing - so I guess I'm not going to skip it, I
guess I'm going to talk about it - is that with the obliquity of the
magnetosphere, the tilt relative to the solar ecliptic plane as Saturn
spins around, it will beat.

And so we're starting to notice a time varying beating going on in
different data sets with different instruments. They're all noticing the
same beating. And so one of the big questions that has come out of
Saturn after four years of studying Saturn is we still can't exactly
convince ourselves of what the daily rotation rate of Saturn is. And
that's a big surprise.

If you think - to me I think of it like some of the fundamental things
that you learn about the Earth or like back 100 years ago when they were
trying to figure out the longitude and latitude, some of these really
important fundamental things, you know, of the planet.

Well at least you know what the length of the day is. And with Saturn we
are having a hard time pinning it down because the rotating - the
rotation rate seems to be different from what was measured with Voyager
spacecraft. And it's even been different - it's migrated in the past
four years.

And so there's a lot of work that's gone into and continues to go into
trying to understand what makes these different measurements so
different. And that's all I'm going to say about that.

I'm going to go on to Page 13. And one of the things that we wanted to
characterize before we - before Cassini's mission started was what they
call Saturn's kilometric radiation. I'm going to in the next few pages
talk a little bit about what is kilometric radiation and the effects
that - what we know about the kilometric radiation, what that has on
this question of what is the length of the day.

So okay. I really want to skip Page 14. We'll come back to Page 14. I'm
going to go on to Page 15 \-- what is kilometric radiation? Well
Saturn's kilometric radiation is what we think of as the analog of
terrestrial auroral kilometric radiation.

And I got a couple of definitions of auroral kilometric radiation. One
is from Wikipedia and one is from Scientific American. Auroral
kilometric radiation is the intense radio emission in the acceleration
zone many times past the - times the distance of the radius of the Earth
where the aurora is.

And basically what happens is that as electrons are spiraling down the
magnetic field line and creating the aurora, they generate waves, which
when translated into the audio regions for the human ear actually sound
like whistles and chirps and other odd noises. So you can actually play
an audio tape of the chatter coming from the auroral zone. And that is
called auroral kilometric radiation.

And in Scientific American they called it Earth's Auroral Radio Chatter.
So it's associated with the aurora. It's associated with the movement of
particles raining down field lines into the atmosphere. And Saturn has a
similar kind of kilometric radiation. And one of the outstanding
questions is still how much of an analog is this for the Earth's auroral
radio chatter? But that's basically what it is.

And now I want to go back to Page 14. No, I don't want to go back to
Page 14 - not yet. Let's go on to Page 16. I guess I have a thought
missing or a page missing, which is that why would the SKR be related to
the beating of the - why is that related to the rotation rate of Saturn?

And what I'm going to say is because it's still - these are still some
of the outstanding questions, is trying to understand the relationship
between the SKR and the beating. But it is beating in a regular fashion
that's very close to the spin rate of Saturn - very close. But it's off
just a little bit.

And now if we go to Page 14, these are all the different measurements,
different kinds of measurements that \-- and you'll see that the
differences are along the bottom is the rotation period of Saturn. And
the green line for example is the Saturn SKI - R period, which is almost
10 hours and 45 minutes.

And you'll see that that's slightly different from the Voyager SKR
period, which was a little bit more than 10 hours and 45 minutes. And we
have tracking of clouds, which is this Anderson and Schubert 2007
measurement which is somewhere around 10 hours and a little bit more
than 30 minutes. And I misspoke on the Voyager one being a little bit
less than 10 hours and 45 minutes.

So you can see all the data shown here on Slide 14 is different, you
know, different measurements that have been made of this. And you can
see that it's - it migrates around but it's about, you know, 10 hours
and 30 minutes - something like that. And trying to pin down which of
these measurements is giving us the right rotation period is one of the
big questions that is outstanding from the prime mission.

So Page 17 is another slide that shows the modulating of certain
measurements with that same beating period. And likewise Page 18 is a
little bit more about the radio measurements that are going around with
periods that are somewhat different from Voyager 1 and 2.

So on Page 19 one of the primary objectives of map science was to
understand Titan, to investigate the upper atmosphere and ionosphere of
Titan and to investigate Titan's magnetospheric interaction. And I'm
actually going to stop here for a few seconds and just inquire whether
there was any questions on the material that I just covered? Yes. We
have a question.

Amanda Hendrix: Okay. I think I have a question about the new radiation
belt inside the D ring.

Claudia Alexander: Yes.

Amanda Hendrix: Go over that.

Claudia Alexander: Not yet. And I'll be honest. I'm not going to cover
every single bullet in the talk, okay? So the new radiation belt I'm
just going to mention that it has also been called basically a ring
current. So it's not - it's got some hot particles but it's not quite a
radiation belt. So but all I'll say is that it's a new region that when
we talk about the regions of the magnetosphere of Saturn, we've got a
new one to add to the lexicon.

Amanda Hendrix: So is it a new region or a region that is new to us
because Cassini flew close to them?

Claudia Alexander: That's correct. That's right. Basically we had no
idea there was radiation inside the D ring. And so we flew closer in and
whoo, there it is.

Amanda Hendrix: (This was) in July?

Claudia Alexander: Yes.

Amanda Hendrix: Okay. And my other question - oh, was back to Slide 4
about - or no. I guess it was - where was it - where I asked before
about the plasma sheets?

Claudia Alexander: Yes.

Amanda Hendrix: So the reason it sort of - it's kind of like a nozzle
shape I guess a little bit or maybe it just touches (all of a
sudden)\...

Claudia Alexander: That's misleading. And it's not quite sudden. I mean
the drawing shows just sort of a line and then a nice little edge and
then it starts to grow out. And that's just the artistic rendering.

Amanda Hendrix: Okay.

Claudia Alexander: That - it doesn't really look like that. And let me
see if I included a page that shows what it does look like.

Amanda Hendrix: And what I'm wondering is does it sort of narrow down
like that because of the neutrals in that inner part of the
magnetosphere? Or there just simply isn't as much plasma because it's
sort of eaten up by the neutrals?

Claudia Alexander: That's correct.

Amanda Hendrix: Okay.

Claudia Alexander: Well the inner magnetosphere is dominated by
neutrals. And that's another big finding. And I hope that I have that
somewhere later. You have to know that I - we're required to turn these
packages in weeks before. And so I turned it in and then I don't
remember what I included in it. So if we can come back to that in a
minute because - let me come back to that when we talk a little bit
about the middle magnetosphere.

Amanda Hendrix: Okay. And I had one more question but I don't want to
dominate in case anybody else has something for right now. Okay. Well my
other question was about the reconnection because when you (showed us
the slide with the images of Earth)\...

Claudia Alexander: Yes. Right.

Amanda Hendrix: \...and you said that then the sort of end step is the
aurora.

Claudia Alexander: Right.

Amanda Hendrix: Is that the same with Saturn? And are there - is there
then an auroral response to solar wind so we can maybe measure
variations? Do you know if anybody has\...?

Claudia Alexander: What I heard today this very week - yesterday it
was - the presentation that (Bill) gave. And just to remind you guys we
are here at a symposium that is discussing Saturn at the end of the
prime mission and what did we learn. And they are - there's some
controversy still about what is the aurora showing. Because it has -
okay, this is a little bit of a side step.

But I think it's a good point and fun to talk about. Earth's aurora is
episodic, okay? So you see it when there's certain weather conditions of
the sun. When the sun and the Earth get connected then the end result of
that is aurora precipitating down. And then it gets cut off and you
don't see it anymore. At Jupiter the aurora is a permanent feature.

Amanda Hendrix: And at Saturn, too?

Claudia Alexander: And at Saturn, too. Okay? So that would suggest that
it all has to do with plasma internal to Saturn and not coming from the
sun. And it has to do with the moons going around and Saturn. But there
are smaller features of Saturn's aurora that have the episodic nature,
that have the substorm-like response that happens after these substorms
seem to be happening.

And so they're still looking for the measurement. When there's a
substorm and one of these plasmoids goes off down the tail, then
Saturn's magnetosphere does a thing that's called technically
dipolarization. So you have these stretched out field lines that look
banana shaped or like a dolphin's nose.

And then in a dipolarization event they suddenly - they snap to a
dipolar - remember I talked about the iron filings and how you have that
dipolar shape like a orange or a - you know. And when it dipolarizes, it
has a tendency to push the plasma down the field lines into the aurora.
So not only are they seeing these signatures in the auroral zone where
they see these episodic brightenings.

But they've measured three separate events, dipolarization events that
they are pretty sure are dipolarization events in the four years of
going around Saturn. So they do think that the sun is exerting an
influence at Saturn. But they don't really have enough - it's not - the
evidence isn't conclusive yet.

Amanda Hendrix: Okay. Interesting. Thank you.

Claudia Alexander: Okay. Where was I before I was so rudely interrupted?
Okay.

Amanda Hendrix: Are we on 19?

Claudia Alexander: We're on Page 19. Thank you for reminding me. Okay.
So we were going to go to Titan now and talk about the two sort of
really, really interesting results. One is that negative ions \-- I'm
just going to read it from Page 19 \-- heavy negative ions were detected
in the ionosphere of Saturn - of Titan. And this is really strange.

And I have to admit when I first heard about this result, I thought what
are they talking about? What is a negative ion? I did not know. And so I
on Page 20 put a definition of a negative ion because always thought
that you had them in atoms.

You have electrons. And if you strip off an electron which is the
negatively charged particle, then what remains of any atom is an ion.
It's a positively charged thing because the electrons are missing. And
that's what it is. So what's a negative ion? I don't get it.

And so what they are talking about in the ionosphere of Titan is very,
very, very heavy particles, so greater than 2000 amu particles. And
these are not really - these are molecules, okay? And what they're
thinking is that they're probably aggregates of what is called
polycyclic aeromatic hydrocarbons or PAHs.

And a classic example of a PAH is a buckyball, who some of you may have
heard of that in astrophysics, which is a big giant molecule that's sort
of wrapped up on itself into the shape of a ball. So that's only an
example of what a polycyclic aeromatic hydrocarbon might be.

And so they discovered these very, very, very heavy things that if they
are aggregates it's easy that they could - it's easy how they could
become negatively charged - that drop down into the lower atmosphere
after being created higher up.

So the picture that we've put together of this is that you have
energetic charge - so now I'm on Page 21 - energetic charged particles
impinging in the atmosphere of Titan. You have dissociation of these
atmospheric methane and hydrocarbons, ionization of the same and then a
glomeration of these heavy particles.

And then they drop down into the atmosphere of Titan. And so this is
cool. This is a very, very interesting discovery because it tells us a
little bit about how complex organic molecules might have originated and
continue to populate Titan \-- the atmosphere environment of Titan. And
so Page 22 - was there a question?

Amanda Hendrix: I was just going to interject quickly, but I think that
we might have a CHARM telecom dedicated to Titan's negative ions coming
up.

Claudia Alexander: Okay. Fantastic. Okay.

Amanda Hendrix: You can hear more.

Claudia Alexander: Okay. Fantastic. I think that's one of the most
interesting of the results. And the whole idea of the chemistry of Titan
so different from the chemistry of the Earth I think is absolutely
fascinating. So I think that would be a very interesting CHARM lecture.

Okay. So on Slide 22, one of the things we needed to understand was the
upper atmosphere and ionosphere of Saturn, and what they call
investigating the sources of what they call Saturn electrostatic
discharges or SEDs. And I'm not going to say much about this even though
I put a lot of the bullets down.

They have noticed fuel to line currents. I've moved on to Page 23. We
show - on Page 23 is shown the aurora which I talked about being a
semi-permanent feature there, which we've seen the downward
precipitating electrons going into the auroral zone.

And we think where they're - we know where they're originating. And so
these are important exploratory types of mapping out some of the
processes that's happening in the magnetosphere that we have
accomplished with the prime mission.

I moved on to Page 24. Okay. We had with Jupiter with the Galileo
mission we discovered quite a few interesting things about the icy
satellites in the Jovian magnetosphere, including discovering an icy
moon that has its own magnetosphere. What a surprise that was.

And so we have wanted to do more exploratory work studying the icy
satellites, their atmospheres and any extended atmosphere or gas clouds
that they may have, and those interactions with the magnetosphere and
the rings. And lo and behold yet another surprise, which is that
Enceladus seems to be active.

It is putting out a plume of water vapor into the - and other molecules
into Saturn's magnetosphere. It was the magnetometer itself that first
noticed this because of the mass loading of Saturn's magnetic field
lines in the vicinity, distorted the magnetic flux in the region, and so
yet again another incredible surprise with an icy moon in a
magnetosphere. And there's plenty more exploration to be done of this
particular moon.

Almost last we discovered that a ring has an ionosphere. So the intent
was to investigate ring magnetosphere and coupling of the rings to the
ionosphere, all those electromagnetic interactions. And it investigates
electromagnetic processes that are responsible for ring structure.

And among the things that we discovered was that there could be a ring,
that there is a ionosphere associated with the ring. So that is Page 27.
And I'm not going to say more than that.

I'm going to conclude with just talking a little bit about what remains
to be done. So I talked about the reconnection being one of the most
important \-- it's actually one of the most important processes in
plasma physics around the solar system and in the interstellar medium.
We see it everywhere and we definitely want to study how it works at
Saturn. And those measurements will be taken in the equinox and Cassini
solstice mission.

Amanda Hendrix: We just had a really big earthquake here in Pasadena.

Claudia Alexander: No kidding?

Amanda Hendrix: Yes. I mean we're in - I'm shaking.

Claudia Alexander: Oh my God. Is everybody okay?

Amanda Hendrix: I mean we're in Building 230 which is like, you know, a
bunker.

Claudia Alexander: How long did it last?

Amanda Hendrix: Oh, 20 seconds.

Claudia Alexander: Twenty seconds? Wow.

Amanda Hendrix: I mean my clocks were shaking off the wall.

Claudia Alexander: Oh God. And does everything seem like it's okay?

Amanda Hendrix: So far. I don't see anything falling off of - yes,
nothing fell off the desks around here. Sorry to interrupt you, Claudia.

Claudia Alexander: Are you a California native?

Amanda Hendrix: Oh well close enough. I used to live on the San Andreas
fault.

Claudia Alexander: Okay. Give us your best estimate of what the
magnitude of it was. Was it five or a six?

Amanda Hendrix: Oh\...

Woman: It depends on how far away it was.

Claudia Alexander: Yes. Let me go on to the USGS.

Woman: Yes. I've got it up now. Yes. They don't have it there yet.

Amanda Hendrix: Oh man.

Woman: I'll hit reload until they give an estimate.

Claudia Alexander: I'm bringing up CNN right here. But if you - just
your sense - so was it like a magnitude\...?

Amanda Hendrix: It's bigger than I've ever felt ever.

Claudia Alexander: Really?

Amanda Hendrix: Yes.

Claudia Alexander: Wow. Wow.

Woman: So it was either really big and far away or not that big a\...

Woman: No. It was here. We're in Southern California.

Amanda Hendrix: Yes.

Woman: It was huge. We're still moving.

Amanda Hendrix: Where are you?

Woman: I'm near Long Beach.

Woman: Okay. So it's down there, because we're not feeling aftershocks
here.

Woman: And where are you?

Woman: In Pasadena.

Woman: Oh you're at JPL.

Woman: Yes.

Claudia Alexander: You guys have to know this stuff.

Woman: I'm hitting reload on the USGS page now. But they don't have it
yet.

Woman: Yes. It's not coming up on the tracker I have either.

Claudia Alexander: I'm hitting reload on CNN.

Amanda Hendrix: Yes. I get the earthquake announcements.

Woman: Well if Long Beach is feeling aftershocks, then it was down there
somewhere.

Woman: Oh there it is \-- 5.16 (ohill) is the preliminary.

Woman: Wow. In a hotel\...

Woman: Five point six.

Woman: Five point\...

Woman: Five point six.

Claudia Alexander: So that disrupted this teleconference.

Amanda Hendrix: Sorry. I'll mute\...

Woman: I'm going to just check\...

Amanda Hendrix: I'm going to mute and you can continue. And maybe
between the talks I'll give an update.

Claudia Alexander: Okay. Let's do that. Okay. Well after that
excitement, I just want to wrap this up. Let me move on to Page 29 and
just say that there were - with the excitement around Enceladus, we
didn't really get a chance to do up close and personal exploration of
Mimas, Dione, Tethys and Rhea.

So there is some interest in doing that. There will be continued
exploration of Enceladus' plume and its interaction with the
magnetosphere. We need to do - there's just so much still to do with
Titan. And I'm just going to leave it at that.

And then the whole inner magnetosphere with the SOI - so we would like
to continue to do what they call proximal science, so the science very
close to Saturn. And that'll be something that will be studied for the
very end of mission.

So with that, I'm going to sort of conclude. The rest of it is the sort
of definitions of things. To answer Amanda's question about the inner
magnetosphere, there is a picture that I left off of this - I left out a
whole discussion of that.

And it was in the previous CHARM talk that I gave about a year ago. It's
the MIMI measurements of the neutrals and it's a wedge shape, a
continuous wedge shape out to about I think 14 RJ - RS \-- something
like that. And exactly how those neutrals and energetic particles
interact with each other to give what's the ultimate shape.

They're just now starting to understand the distribution functions and
the - it behaves a little bit like a comet where the ring distribution
is how it initially is distributed. And then it ends up changing the
distribution function of the charged particles. But all that is still
tentatively mapped out.

It's not, you know, we don't I think have a much better picture. We know
it doesn't make a sharp angle. That's an artist's rendering. But I don't
think we have a really good picture yet of how that region, the
different populations of charged particles, how they interact with one
another.

Amanda Hendrix: Okay. Interesting enough. Thank you. Okay. So we have -
yes. So there's different magnetospheric related backup slides that
Claudia put in here. So this is great. And does anybody have any
questions for Claudia right now, because we'll move on to the Titan
section.

And people can ask questions about the magnetospheric stuff at the very
end as well. But does anybody want to jump in with a question now?
Please do so. Otherwise we'll get into Titan with\...

David DelMonte: Hi.

Amanda Hendrix: Hi.

David DelMonte: It's David DelMonte here. I'm sorry about the
earthquake. It seems to be rather large to LA as well as Northern
California.

Claudia Alexander: Really?

David DelMonte: Yes.

Claudia Alexander: Jesus.

David DelMonte: Yes. My daughter is in Los Angeles. A quick question.
The slides are fascinating. Are they for public dissemination? Can we
use some of them in our presentation?

Claudia Alexander: Do you mean the artists's rendering, the group of
slides that are in the appendix?

David DelMonte: Just the PD - some of the slides in the PDF generally
and some of the photos.

Claudia Alexander: Okay. Yes, I believe that all of this is for public
consumption.

David DelMonte: Okay. Thanks.

Claudia Alexander: The whole package.

David DelMonte: And good luck to everybody out there.

Amanda Hendrix: Dr. Elizabeth Turtle, are you ready?

Elizabeth Turtle: Sure.

Amanda Hendrix: Okay. Let's start on Titan. And I think that we're on
Slide 39 now, for everybody who's listening in.

Elizabeth Turtle: I'm going to give an overview of what we've seen on
Titan in the last year. Slide 40 has a list of the Titan flybys that
occurred in the last year, which is the 34th through the 44th, so 11
close flybys to Titan. And I've just listed their dates and also what
happened basically at closest approach during each of these encounters.

You can see - and I've used the abbreviations for the instruments here.
But VIMS, the Visual and Infrared Mapping Spectrometer, had high
resolution mapping on a number of these flybys. And the radar instrument
got synthetic aperture radar strips on several of these flybys.

And as well also at closest approach the ion and neutral mass
spectrometer takes data, actually sampling the upper reaches of Titan's
atmosphere. So those instruments typically are the ones that are most
common as you can see here, most commonly make observations at closest
approach.

But if you go down to the next slide, Slide 41, you'll see an incredibly
busy representation of all of the Titan flybys in the nominal mission.
And this is just to illustrate just how much is going on on Cassini
during these encounters. You know, I've kind of listed the highlights in
Slide 40.

But Slide 41 really illustrates in much more detail what's going on. So
reading across each line, each colored line with, you know, they have
lots of colors on them. Each of those is a single encounter. And each
color represents a specific instrument.

You can actually kind of - if you can make it out. It's not terribly
high resolution through the PDF through the PowerPoint into the PDF
again. But each color represents a different instrument. You can kind of
make out which instruments those are.

And then it's just a time going through the - as you go across, it's
just a time going through the flyby. And then as you move down each line
is representing a different flyby. And generally we actually observe
Titan for 12 to 24 hours before and after closest approach.

And you can see kind of in this pattern that some of the instruments are
more likely to observe on near closest approach or as we're further away
from Titan depending on the specific goals of that instrument. So this
slide represents an awful lot of work on behalf of an awful lot of
people and arguing or negotiating maybe I should say back and forth.

But there's really a lot going on. And that's what led to the results
that I'm going to discuss in the upcoming slides and the papers that are
really starting to stream out from the Cassini mission.

I think it was mentioned right when I connected into the telecom,
someone was talking about the books that people are working on. And in
fact there's a meeting this week. There was the one about Titan just a
couple weeks ago. So there's a lot of synthesis of all of the four years
of data we have going on.

So on Slide 42 I've shown a recent image. And in fact there was another
one released just yesterday of some clouds near the North Pole on Titan.
Titan's season is currently moving toward northern spring. When Cassini
arrived in July '04 - so just four years ago - it was essentially the
equivalent of mid-January, about the 12th of January on Earth, so
northern winter.

And in the last four years, Saturn - the Saturnian system and Titan
itself has moved almost towards spring. So in the last four years we've
basically gone from the 12th of January to the 8th of March. So we're
coming up on the vernal equinox.

And as we - as the seasons are changing on Titan, we're seeing changes
in the distribution of the clouds, changes in the meteorology as of
course we do here on Earth. When Cassini arrived, we were seeing a lot
of intense activity of conductive cloud cells at the South Pole. And
those basically disappeared at the end of 2004. There haven't been many
big outbursts at the South Pole seen since then.

We have been seeing clouds at higher and higher southern \-- lower and
lower I should say \-- southern latitudes, but kind of these streaks.
And now that the North Pole is kind of coming out, it's being
illuminated. As the sun moves further north, that area is illuminated.

We're seeing these clouds up at about 60 degrees north latitude quite
consistently actually. Now of course we're only getting snapshots for
the most part with Cassini or we have been. If you go back to Slide 40,
you know, in those four \-- in the whole last year we've had 11 close
encounters with Titan. So it's about once a month roughly.

And that's just kind of, you know, if you were trying to predict the
weather on Earth for example and you were only getting an image every
month, it might be hard unless you live in someplace like Arizona or
Sourthern California where the weather stays the same all the time.

We're now - there are ground-based, Earth-based monitoring programs and
we're now instituting something similar on Cassini where basically any
time there's a space in some of the observations we actually are just
turning the spacecraft to look at Titan and just take pictures, try to
get a few pictures every week so we just can monitor the weather a bit
better and watch how it's changing as we move into spring.

And in fact there was a big - a fairly big outburst this spring between
a couple of the Cassini Titan encounters that was observed by
Earth-based observers. So we're hoping to catch more of those. But
anyway I wanted to illustrate that we're seeing the meteorology changing
with the seasons on Titan.

Something else on Slide 43, something else that we're tracking is the
haze on Titan. This shows a series of observations, three different
observations taken at different times; clearly very different phase
angles. The one on the bottom left the sun is basically behind the
spacecraft and the one on the bottom right the sun is basically behind
Titan. As seen by the spacecraft you can see this detached haze kind of
a ring around the upper reaches of Titan's atmosphere.

And that's something that was also observed by Voyager. But one of the
things that's interesting is that we're seeing it at a rather different
altitude. It was at about 300-350 kilometers when Voyager flew by and
it's currently, what the Cassini spacecraft has been observing is at
about 500 kilometers. So it's actually substantially higher.

And it'll be interesting to watch, again, as the - as Titan moves into
spring, which is the season when Voyager II - Voyager I, I'm sorry,
encountered Titan, also Voyager II, that - it'll be interesting to see
if this changes, if it's a seasonal effect or if something else has
changed the altitude of this haze.

Amanda Hendrix: So is the haze glare, is it global then?

Elizabeth Turtle: Yes. Yeah.

Amanda Hendrix: But the altitude of it might change with seasons?

Elizabeth Turtle: Well, that's what we're not sure of because the
altitude, we have, you know, we have the Voyager data from 1980, which
was the equivalent of - it was just after spring on Titan. And Cassini
has been there and has been observing the haze at about 150 kilometers
higher altitude.

And now we're approaching the same season. So as we move into the
extended mission with Cassini we'll be able to watch and if the
spacecraft and things continue long enough maybe we'll actually overlap
the same season as the Voyager encounters. And if so and the haze is
still at a different altitude then it's not purely seasonal.

Amanda Hendrix: Yeah. Okay. Thanks.

Elizabeth Turtle: So, yeah, so it's interesting and may indicate that
something more complex than simply a seasonal change is going on in the
atmosphere.

The 44th slide illustrates the - is a map of Titan that was released
last October. We're continually updating these maps and there is more
territory that has been filled in in more recent encounters. But this is
the most recent one we've released. It takes a lot of work to process
the images of Titan to remove the atmospheric effects to the extent
possible. And you can see a lot of seams in this map.

A lot of the other - the maps of the other satellites look much cleaner
and part of this is because of the complicating effect of the haze and
how much looking - how much different processing you have to apply when
you're looking at Titan under different geometric conditions, different
illumination angles.

And in fact it's proven surprisingly difficult to handle adding in the
north - high northern territory. You can see that most of our coverage
in this map from last fall is below 60 degrees north latitude. And a lot
of that is because of the - because it's been northern winter and the
illumination is only moving up that far.

But it's also much - it's hard to process those images in a way that we
can seamlessly move them into this map. And we do, in fact, now have
coverage of the North Pole at near infrared wavelength. The scattering
in the atmosphere helps because there's so much scattering that it - the
surface is actually illuminated beyond the terminator.

And we can actually see - see about 10 degrees beyond the terminator. So
we've imaged the North Polar Region now but it's just been hard to add
into the map. So we'll be updating that as we can. But we have basically
global coverage of the surface of Titan with the exception of some of
the high - the highest northern territory.

And this is, again, this is a near infrared map, this is made by the
Imaging Science Subsystem, ISS. A lot of the mapping until now as the
sun has began illuminating the surface - a lot of the mapping has been
done by the radar instruments. And that, on Slide 45, shows that
coverage. This is a very false color image from the radar instrument
illustrating the distribution of lakes on Titan at Titan's North Pole.

So the dark blue areas, the blue - the areas that have been colored blue
here represent areas where liquid is expected to be on the surface based
on the radar evidence. And so you can see there's quite a variety of
lakes and the coverage of the North Pole is, by the radar instrument, is
being increased - there are several flybys.

The next slide - there's actually, I should say, there's a URL at the
bottom of this page, there's a movie associated with this release, with
this image here but you can follow that link and download a movie of
this territory.

The right-most radar swath fills in some coverage of Kraken Mare, which
is an 1100-kilometer long lake or sea, I guess, on the surface of Titan
at high northern latitudes. And this was actually discovered in early
2007. Slide 46 has a couple of images taken by the ISS, the camera on
Cassini, on the left, showing this kind of squiggly dark feature that
extends for 1100 kilometers across the surface of Titan at high northern
latitudes.

Again you can actually see some cloud streaks in this image as well from
February 2007. Soon after that radar also observed - or about that same
time radar also observed the very northern tip of Kraken Mare and the
image on the right kind of outlines - the blue outlines the dark areas
that were seen by the camera in the near infrared. And then you can see
how those overlap in the radar.

And so the - on Slide 45 you can see that that right-most radar swath
has now covered another piece of Kraken Mare a little further south kind
of filling that area in. I'll also mention while looking at slide -
pardon? Was there a question?

Amanda Hendrix: No. I think you were just breaking up a little bit
though.

Elizabeth Turtle: Oh weird, okay.

Amanda Hendrix: Can you just say that last little bit again?

Elizabeth Turtle: About\...

Amanda Hendrix: Well, after you were talking about how you filled in
that one region again.

Elizabeth Turtle: Right, okay. So there's - so the radar has now gotten
another slice of Kraken Mare further south. Also while I'm on this slide
I'll point out you can see that the North Pole is kind of not covered by
the radar so far and there's actually a lake seen just below the North
Pole as it's oriented in this image.

And ISS just a month ago or so actually has gotten some images that show
the edge of that - the other edge of that lake kind of closing around
that lake towards the North Pole. So we're filling in that territory and
mapping out the northern lakes with a combination of both of those
instruments.

So Slide 47 is another image of the North Polar territory. And in two of
the radar swaths actually overlap in such a way as to create stereo -
basically a radar stereo pair. And what's shown at the bottom here is
the topography derived from that stereo.

And the red areas are high and the blue areas are - the blue and the
purple areas are low. And some of those, in fact, are crossing the top
of Mare Kraken, you can see there's kind of island at the very top of
Mare Kraken and that's kind of standing out. It was fairly high
topography - relatively high topography standing up above that lake.

So the radar instrument can also, in addition to having a mode that
measures the altimetry, can actually get stereo and more high-resolution
topography like this in areas where the swaths overlap. And this is one
of the first high-resolution topographic maps of Titan, which is really
interesting and will help interpret the geology of the surface, the
drainage patterns for example.

Having the slope information helps understand how the - how liquids are
draining across the surface into the lake and we can get the height of
the lake, the relative height to try to understand the methane table and
the methane cycle on Titan.

Now until recently radar hadn't really been able to see high southern
latitudes. This last year was the first time that the radar instrument
actually got star data of high southern latitudes. Until now it had been
mapping out the North Pole. But because of the geometry of the
encounters they hadn't had any South Polar coverage yet.

But in October and then again in December there were some radar
observations during - when Cassini was passing near Titan's South Pole.
The one of the left from October is showing territory at about 70
degrees south latitude. And you can see that there are a couple - there
are two or three features - three features that have been identified as
possible lakes at that latitude.

In December there was actually a close flyby where radar has got a swath
of data that covers the South Pole itself. And you can see in this case
that there are two areas they've identified as Cassini liquid - as being
lakes.

If you go down to Slide 49 you'll see the same image - the same radar
image of Titan's South Pole on the right. And a near infrared image from
the ISS instrument on the left. And in fact this observation on the left
is one in which ISS suggested that the feature near the bottom, it looks
kind of like an upside down footprint, might be a lake. And that is
indeed named Ontario Lakus because it's about the size of Lake Ontario.

Of course the camera has been able to - the VIMS instrument and the ISS
instrument have been able to image the South Pole when we've had the
favorable geometry because it's been completely illuminated. And you can
see that there's actually quite a lot of variation in the surface
brightness.

The very bright material near the top is actually clouds in the
atmosphere. But the dark and the very dark features and the gray are
actually the surface. And this is quite an old observation taken just
from - just about a year into the mission. But it provides a very
interesting comparison with the radar observation at the South Pole
because not all of those dark features appear to be lakes at this time.

Now clearly a fair amount of time has passed on Titan and so one of the
possibilities is that they're changes. Another possibility is simply
that what we're seeing as dark in the ISS image is not always liquid.
And that's of course true at the equator as well. In the near infrared
the equatorial regions have very large expanses of dark material and
that's actually solid sand - not - well, dunes of hydrocarbon solid
material, particulate material.

And so it may be similar here that some of these areas are maybe not
dunes but also places where there is solid accumulations of hydrocarbons
instead of liquids and they're not showing up as liquids in the radar
data.

But it's a very intriguing comparison and something that we're really
looking forward to getting more data of in the extended mission and
hopefully even further on to try to make this comparison and understand
better what we're seeing with the different instruments.

And to see if we're seeing evidence for changes on the surface, which is
another possibility especially given that we've seen large clouds just
since there early on and there might have been - there might have been
rain and since those have dried up perhaps it's not raining as much.

Another thing - another comparison between some of the early
observations of the South Pole and the recent radar observation is shown
on the 50th slide. This shows, in fact, an image that was taken
during\...

Trina Ray: Hey, Zibi?

Elizabeth Turtle: Yes.

Trina Ray: Yeah, Amanda had a question.

Elizabeth Turtle: Oh, okay.

Amanda Hendrix: Sorry, we muted on accident and I was - can we go back
to 49?

Elizabeth Turtle: Sure.

Amanda Hendrix: I just wanted to make sure I understand so did you say
that the red plus indicates the South Pole?

Elizabeth Turtle: I did not say that but you have correctly interpreted
that. I should have said that. The red plus is about where the South
Pole is, yes.

Amanda Hendrix: Okay.

Elizabeth Turtle: And these - I should also say these are very different
scales. So the very dark feature that you see, the blue feature that you
see in the - in the radar observation is actually the dark feature
that's at about 7 o'clock below the red plus, it's not all the way down
at Ontario Lakus.

Amanda Hendrix: Is Ontario Lakus the kidney bean shaped one in the
image?

Elizabeth Turtle: Yeah, at the bottom of the image, yep. And that's
about - just for scale that's about 237 kilometers - 237 kilometers long
if I remember correctly.

Amanda Hendrix: And so is that one that you're saying doesn't show up in
the radar?

Elizabeth Turtle: Radar hasn't observed it yet.

Amanda Hendrix: Oh, okay.

Elizabeth Turtle: It's not in the radar\...

Amanda Hendrix: Out of the - it's out of the swath kind of here.

Elizabeth Turtle: Right. It's not in the radar swath. I think - I know
they get that in the extended mission but I'd be guessing at which flyby
it is. But I know they do get to observe it during the extended mission,
once - at least once if not twice.

Amanda Hendrix: Oh, and then so\...

Elizabeth Turtle: So we still get radar data of that. And VIMS actually
had a really high-resolution view of Ontario Lakus also last December.
And so they're analyzing the spectra of that. And I think there's a
paper that's due quite soon to come out in maybe Nature, by (Bob Brown)
about it.

Amanda Hendrix: Oh, okay. But then the lake that you can see, you know,
partially in the radar image\...

Elizabeth Turtle: Yeah.

Amanda Hendrix: \...where does that correspond to in the ISS image?

Elizabeth Turtle: Right, if you look at the ISS image where the South
Pole is at about 7 o'clock beneath it you see it's kind of just gray - I
should have highlighted this, I'm sorry. It's kind of gray right beneath
the plus sign\...

Amanda Hendrix: Okay.

Elizabeth Turtle: And then it gets dark again. The very dark feature in
the radar is that kind of diamond shaped\...

Amanda Hendrix: Oh, okay.

Elizabeth Turtle: \...very dark feature in the ISS. It's just the edge
of that.

Amanda Hendrix: Oh got you, okay. And then can I ask another question
while I have you is that back on 47 about the topography?

Elizabeth Turtle: Yep.

Amanda Hendrix: So I think this is really neat because I haven't seen
any radar topography before. But the - so in the two swaths down at the
bottom, they're both radar. And so the way I'm interpreting this is that
the kind of medium dark area over towards the left is actually a deeper
region than the super dark area that's by the little cut out more in the
middle.

Elizabeth Turtle: Yeah, I don't know\...

((Crosstalk))

Elizabeth Turtle: \...I don't know what the uncertainty is on this,
there aren't error bars on their legend.

Amanda Hendrix: Because\...

((Crosstalk))

Elizabeth Turtle: It looks like it's about the same or do you mean way
at the left?

Amanda Hendrix: I don't mean way at the left I mean sort of that sort
of - let's see. So, it's kind of just to the left of center of the whole
entire swath.

Elizabeth Turtle: Yep, yeah, it looks - it does look more\...

Amanda Hendrix: It's purple in the topography and it's just kind of
grayish in the regular radar image.

Elizabeth Turtle: Yeah.

Amanda Hendrix: And then - but then the area to the right of that that's
really dark in the radar image is more blue. And so I always kind of
picture in my mind that the really dark regions in the radar images are
deeper maybe but that's probably the wrong way to think about it.

Elizabeth Turtle: Right. The really dark regions in the radar images
are - where basically no signal is coming back to the spacecraft from
the radar, so - or coming back to the radar. So it basically means that
all of the signal sent out from the radar is reflected away so that's
actually more an effect of the surface properties than the topography.

Amanda Hendrix: Right, okay.

Elizabeth Turtle: Now obviously you'd expect that the lowest areas to be
the ones that have liquids. And that's something that the radar team is
working on right now. And again, I think there's a paper being written
about it right now.

The methane table, the equivalent on Titan of the water table on Earth,
what it is and whether the lake levels are actually the same - the water
levels - not the water levels, I'm sorry, the methane levels are the
same in all of these lakes or whether they differ because if they differ
then that suggests no connectivity or less connectivity between the
lakes within the subsurface of Titan.

Amanda Hendrix: Oh, right.

Elizabeth Turtle: And so that's important for understanding what the
transport of methane within and under the surface of Titan. So that's a
really good - it's a really good point. Not all the lakes may be at the
same level and that's something they're analyzing.

Amanda Hendrix: Okay, that's neat. Thanks.

Elizabeth Turtle: Sure. Let's see, so on slide 50 we have another
comparison of the radar here actually on the far right - I'll interrupt
myself. On the far right you can actually see that - the radar swath
where that little dark area matches up with the diamond shaped dark area
we saw on the near infrared.

So this - the imaging observation that's underlying here that's on the
left - the middle and underlying on the right, is - was taken just after
Cassini went into orbit around Saturn; this is just after Saturn orbit
insertion on the T-0 flyby, which is actually a very distant flyby. But
the camera actually can get pretty decent resolution of the surface - of
features of objects even at 100,000 - this is actually at 300,000
kilometers range.

And you can see at the top there's this dark feature, which is named
Mezzoramia. At the bottom of this image there's actually a lot of really
bright stuff again, which is one of those large cloud outbursts. And
you're seeing some of the dark features and the gray of the surface
beneath it.

But leading into Mezzoramia, at the top you can kind of see this dark
channel feature that had been pointed out by ISS and that's kind of
outlined in red in the center image. And on the right you can see that
the radar image actually covers this area and you can see the detail
that the radar instruments can reveal because it gets much higher
resolution than ISS could get on this distant encounter.

On the 51st slide you see that - I put in that radar swath again at -
just blew it up a little bit so you can actually see much more of the
detail. And you can see how channeled the surface is.

There definitely has been liquid flow on the surface of Titan, which is
another piece of evidence that really supports the interpretation of a
lot of these dark features on the surface as liquid - as lakes because
clearly water has been flowing on the surface, carving the surface into
river channels and ponding in areas. So we're looking forward to more
observations of the high southern territory with the radar instrument as
the extended mission progresses.

The 52nd slide shows a couple examples of tectonics. One thing that is
really actually lacking from Titan is large tectonic structures or
global tectonic patterns. If we look at many satellites, you know,
Dione, Rhea even, well Tethys and Enceladus you can see evidence of the
antigenic processes in the deformation of the surface.

You can see that the geologic processes have been modifying the surface
of the planet. And we would certainly expect that to occur on Titan as
well. But there's not a lot of evidence for it. And some of that is
because Titan, like Earth, is - undergoes erosion from liquids flowing
on the surface, from material blowing across the surface just like we
have here on Earth.

And so that erodes tectonic features. But it is - I find it particularly
intriguing just how little we've seen in the way of tectonics.

There are a few features revealed here that are quite linear. Often you
see mountain chains aligned on Earth or other planets and that's an
indication of tectonic activity. And so here on the right is actually a
much older image, which is one of the ones where some mountain chains
had been observed.

And on the left is a very recent image, just from this past May, showing
some other mountain chains, kind of three parallel ones running across
the center of that image. The bright rough terrain or the rough terrain
that is revealed by brighter radar albedoes. So these are about - you
can see that those chains, based on the scale by each of range was about
50 kilometers across.

And the topography on Titan isn't actually terribly high. These are
referred to as mountains often but they're typically a kilometer or so
high, which is still pretty rugged and not an easy place to land.

Amanda Hendrix: And in that image on the left, is that circular feature
a lake?

Elizabeth Turtle: The - I do not believe so. I don't remember - this is
not one of the high latitude passes. And\...

Amanda Hendrix: (Might that be an) impact crater?

Elizabeth Turtle: It is suspiciously circular. In order for it to be
identified as a lake it has to have really low signal. And you can
actually see - it's dark but it's still gray, it's not, you know, a
complete absence of signal, which is really what - almost absence of
signal, which is what you'd expect from a lake.

The fact that it is circular might suggest that it's - it has an impact
origin. It certainly doesn't look terribly fresh because the other
features around it - you don't see an ejecta blanket or something like
that, which you would expect if it were a fresh impact crater.

But, again, Titan, like Earth, has a lot of erosion going on and the,
you know, if you compare the moon, our moon to the surface of the Earth,
the Earth basically has, you know, very, very few impact craters, only
about 150 compared to the moon, which is covered with them. And that's
because of the erosion and Titan is very similar.

So an image like this, it's very hard to tell what that feature is,
which is - leads to lots of speculation. But it is - it has potential.

That actually leads very well into the next slide, Slide 53, which shows
a couple of impact craters observed on Titan. As I mentioned, Titan
doesn't have a lot of impact craters. I think maybe there are five
officially - there really are only a handful of impact craters that we
can fairly confidently identify as impact craters on Titan, which is
very surprising and just attests to the amount of modification of the
surface of Titan.

The one on the right, again, is one of the earliest - in fact this is
the second impact crater identified on Titan. It's an 80-kilometer
diameter crater named Sinlap. The one on the left was also observed just
in a radar flyby last May and that's about 112 kilometers across.

And you can see here - so these are rather bigger than the circular
feature that was revealed in the previous image. But you can also see a
lot more of the structure; you can see that these are depressions with
rugged rims. Sinlap on the right, there's this bright halo around it,
which may be part of the ejecta that's been eroded or is being buried by
the dunes that you can see kind of wrapping around Sinlap.

There's - there are hints of an ejecta blanket around the crater on the
left. But it too is somewhat degraded; it's not a pristine crater the
way we see on the surfaces of most of the icy satellites in the
Saturnian system.

On the 54th slide there is - there are a couple of images, a distant
image taken last fall of the region above Adiri. Adiri is that bright
feature in the middle of all the dark features that are running along
the equator. The North Pole is just slightly to the left of up in that
left hand image.

Just for reference the Huygen's landing site is actually at the kind of
end of that finger that points out toward the eastern end of Adiri. And
we got one of our best views of this region with the ISS camera last
fall. And then again this May we got a very high-resolution view and
that's shown on the right.

And right above Adiri you can see this is a bright feature with a dark
center and then a kind of grayish halo. And that looks like an awful lot
in the near infrared the way Sinlap - and I didn't put that comparison
in - but it looks a lot in the infrared the way Sinlap, which is the
crater on Slide 53 on the right hand side - the way it looks in the
infrared.

And so this is a feature that we think is likely to also be an impact
crater. But we don't have the topographic information so we're going off
the albedo information. But because it looks so much like Sinlap we
think this feature may also be a crater. It's about 90 kilometers in
diameter.

Amanda Hendrix: Is that the same as the Sinlap one?

Elizabeth Turtle: It's about the same; Sinlap's about 80. And Sinlap too
is right down in one of these dark dune-filled regions. So this is in a
very similar territory on the other side of the planet. So but like I
said they're really - and certainly in the last year we may have
identified two more craters on the surface of Titan, there are not a
lot.

One of the other really exciting discoveries in the last year is
illustrated graphically on Page 55. And that is that Titan has - and
likely has an interior ocean. This is a discovery based on all of the
years of observation that went - that came before.

And basically the way it was discovered is that the radar team, as they
were aligning their maps, the different radar star strips, which you can
see kind of intersect because they're these noodles that run across the
surface. And so there are these little strips covering the surface. And
they line them up to map out the surface.

And they were finding that they weren't quite in the right places. The
later ones compared to the earlier ones were off in places by up to 30
kilometers or so. And the model they were using to predict what part of
the surface they were observing at any given time was based on the
rotation inferred for Titan and accounting for the gravitational
influences of Saturn and the large satellites and all of the large
gravitational influences.

But couldn't account for this shift of tens of kilometers of the regions
on the surface relative to where we thought they were. And the way to
explain that is that there's actually enough momentum in Titan's
atmosphere that it is affecting the surface, the rotation or the motion
of the surface relative to the interior of Titan.

But the only way for something like the atmosphere to actually be able
to affect the rotation of the surface is if the surface itself is
decoupled from the interior - from the core by a liquid layer. And so
that indicates that there is an ocean deep within Titan.

It's not - we can say that it's not likely to be too shallow based on
the morphology of some of the surface features especially the impact
craters. They're particularly useful for estimating the thickness of icy
(lithos balls), any lithosphere because impact craters actually can, the
very large ones like Minerva on Titan, which is a few hundred kilometers
across, affect the deep subsurface as well and are affected by the deep
subsurface.

And so if, you know, if there were a very thin layer - surface layer on
Titan above an ocean then it would be easy for such a large impact to
have punched through. So the fact that that didn't punch through, that
it impacted into a solid surface implies that the lithosphere or the
crust on Titan has to be, you know, 100 kilometers - on the order of 100
kilometers thick.

But nonetheless, the fact that the surface is shifting indicates that it
is a solid icy surface over a liquid layer above the interior core. So
that's really - that's a really exciting discovery. And it will actually
be followed up on a by a gravity pass that the T-45 - so the first Titan
encounter of the extended mission is coming up at the end of this month.
I guess that's now. Wow, I don't know how it's the end of July already.

Yeah, so that's - that's just coming up the end of this week. And it's a
pass that the radio science instrument is actually - the prime
instrument, as we call it, at closest approach and that's to detect
the - to get detailed information about the gravity, the interior of
Titan based on its - the gravitational attraction that Cassini feels as
it flies close to Titan in this encounter. So that will really add to
our interpretation of the interior of Titan as well. And the last\...

Amanda Hendrix: Can I ask a question?

Elizabeth Turtle: You sure can.

Amanda Hendrix: About the ocean - is the evidence for the ocean, first
of all, is it just the radar team? And secondly, how similar is that
evidence to the evidence that came up with Jupiter's moon Europa?

Elizabeth Turtle: I think the - well, the strongest evidence for an
ocean in the interior of Titan is this shift in the surface, that over
four years there's actually a 30 kilometer shift in the locations of,
you know, in that the ice shell has rotated so differently from what one
would predict for a solid body that features on the surface are 30
kilometers different from where you would expect them.

That's the, I guess, the most solid evidence, if you will, of a liquid
layer. There - the radio science team and the navigation team are also
studying the interior of Titan based on the gravity felt by Cassini
during encounters with Titan. And of course there have been a lot of
encounters with Titan. And a few of them so far, and the one coming up
this week, have been devoted to radio science.

But I - but they're looking at the bigger structure and can't
distinguish - they don't have the - I can't think of the word. They
can't resolve it, if you will, that's\...

((Crosstalk))

Amanda Hendrix: Yeah, the moment\...

((Crosstalk))

Amanda Hendrix: They can't resolve it with moment of inertia data.

Elizabeth Turtle: Exactly.

Amanda Hendrix: Yeah.

Elizabeth Turtle: Exactly.

Amanda Hendrix: Okay.

Elizabeth Turtle: There are also the - a lot of models that suggest that
Titan should have a liquid layer. The models of the thermal evolution of
Titan would suggest a liquid layer as well, a deep liquid layer. And in
fact that's also predicted and magnetometer data has demonstrated that
at Ganymede around Europa and also Calypso.

Amanda Hendrix: But they don't have the magnetometer data yet for Titan?

Elizabeth Turtle: Right and it's much harder to do that for Titan
because you can't get very close to Titan.

((Crosstalk))

Elizabeth Turtle: The Galilean satellite\...

Amanda Hendrix: Yeah.

Elizabeth Turtle: The Galilean satellites you can get right down close
to the surface with a\...

Amanda Hendrix: Yeah.

Elizabeth Turtle: \...but for Titan we can't get really within 900 - 950
kilometers is the closest we've been

Amanda Hendrix: Yeah.

Elizabeth Turtle: And so the magnetometer is kind of hampered by the
fact that we're so far away from Titan.

Amanda Hendrix: Right.

Elizabeth Turtle: I think on the 70th flyby, the last flyby of the
extended mission, the plan is to get Cassini as close to Titan as
possible and that's at about 900 kilometers if I recall correctly.

Amanda Hendrix: Right.

Elizabeth Turtle: So that will help with the - that may help but it's
going to be harder for the magnetometer team. It's also harder for the
gravity team.

Amanda Hendrix: Right.

Elizabeth Turtle: That's one of the reasons that we can't get as good
gravity for Titan simply because we just can't get that close.

The evidence for an ocean in Europa, there are multiple lines of
evidence. One is simply based on the surface morphology. A lot of the
features on the surface are consistent with a thin ice shell. Again the
impact craters are particularly diagnostic and two of the largest impact
craters on Titan - on, sorry - on Europa have lots of\...

Amanda Hendrix: And\...

((Crosstalk))

Elizabeth Turtle: \...surrounded by concentric (drobbin). The crater
itself was surrounded - in fact there isn't a crater so much as a
disrupted area with lots of concentric (drobbin). And that would be
consistent with impact into an ice layer that's only 30, you know, 25,
30 kilometers thick.

And so the evidence that we don't have ice that thin on Titan is that we
don't see that morphology that we do on Europa. There's also
magnetometer evidence for Europa as well.

Amanda Hendrix: Right.

Elizabeth Turtle: I don't think the - I don't think we have evidence of
non-synchronous rotation for Europa the way we do for Titan though.

Amanda Hendrix: It's in the stress field. It took many, many, many
measurements to sort of get the stresses and then the various crack
patterns are consistent with the stresses that you would get with a
non-synchronous rotation.

Elizabeth Turtle: Yes, it's cycloidal fractures on\...

Amanda Hendrix: On Europa.

Elizabeth Turtle: \...it's like the cycloidal fractures on Europa, it's
very hard to explain those except with a thin ice layer that fractures
easily and, you're right, and that does show non-synchronous rotation
over a much longer time scale, yes.

Amanda Hendrix: Right.

Elizabeth Turtle: Yes, right. I don't think we have the direct evidence
within, you know, a single - within different mission of the time scale
changing. But over the geologic history of Europa there is evidence for
the non-synchronous rotation. Thank you.

And the last slide we're simply looking ahead to the next year where we
have 13 more flybys including T45, which is the 31st. So there's a lot
to come and that's just the first year of the extended mission. So I
will leave it there and take questions if there are more questions.

Amanda Hendrix: Great, thank you. Anybody have questions? I have a
couple.

Elizabeth Turtle: Is anybody still there from Los Angeles?

Amanda Hendrix: Yeah. We hope the Los Angeles people are doing okay.

Elizabeth Turtle: I hope so.

Woman: Yeah, they downgraded it to a 5.4 and there's no reports of
damage.

Elizabeth Turtle: Oh, interesting.

Woman: It quieted down - it quieted down here.

Elizabeth Turtle: Okay, that's good. It says 5.8 on the data I have.

((Crosstalk))

Woman: Yeah it felt big.

Woman: Yeah, I just reloaded it and it went 5.4.

Woman: It felt big.

Elizabeth Turtle: Yeah.

Woman: Yeah. I bet.

Amanda Hendrix: Hey. A couple quick Titan questions I had and I hope
other people ask questions if they have them too. But, Zibi, you said
T-45 is the first - that's the first in the extended mission, right? But
that's the one that's at the end of the week?

Elizabeth Turtle: Yep, that's the 31st.

Amanda Hendrix: Okay.

Elizabeth Turtle: Yeah, the nominal mission went through T-44.

Amanda Hendrix: And then back on slide - the next to the last slide with
the ocean, what are we looking at there? I just want to make sure I
understand.

Elizabeth Turtle: Right. I think, as for the brown I think is the
atmosphere kind of overlying the surface, you can kind of see the
surface at the edges. The kind of mucky brown that's on the outside of
the planet. And then there is - there are a few different layers,
the\...

Amanda Hendrix: The light blue layer underneath the brown surface and
then a dark brown layer, which I presume is the ocean\...

Elizabeth Turtle: Yeah, the dark blue layer is the ocean. I think the
light blue layer is the subsurface layer so the one that's probably on
the order of 100-200 kilometers thick. And then the white layer is
another solid ice layer before you get down to the rocky - centrally
rocky metallic mixture in the core or in the deep interior.

So the - it's an intriguing distinction on Titan and probably Ganymede
as well compared to another interesting comparison to Europa. On Europa
the water layer is probably in contact with the silicate material in the
interior of Europa whereas on Ganymede and on Titan the water layer
actually is above - the liquid water layer is above an ice - a water/ice
layer before you get down to the silicate and metallic material in the
deep interior.

Amanda Hendrix: Oh, okay. Interesting.

Elizabeth Turtle: So that may - that certainly will affect the chemical
evolution of the liquid layer, the liquid water\...

Amanda Hendrix: Right.

Elizabeth Turtle: \...not being in contact with the silicate.

Amanda Hendrix: And is it thought that the - there's a metallic only
core or is it that the core - or it's differentiated such that the core
and silicate are - I mean, sorry, it's a silicate/metallic core mix?

Elizabeth Turtle: That's the kind of question that the moment of inertia
data, the gravity experiments can try to help to answer if they get
potentially high enough resolution the extent to which the mass in the
interior of Titan is concentrated in the core or distributed without -
is distributed more generally in the interior. I don't know the answer
to that. I'm not sure that we have the data to answer that yet.

Amanda Hendrix: Okay.

Man: Can I ask a question?

Elizabeth Turtle: Please.

Man: Thank you. Best case scenario and funding issues aside, what's the
possible lifespan of Cassini?

Elizabeth Turtle: One of the great things about the Saturnian system as
compared to the, you know, the experience we had with Galileo in the
Jovian system is that the radiation is not that the radiation
environment in the Jovian system. So that's not degrading things as
quickly as happened for poor Galileo.

The current plan is for a two-year extended mission, which will take us
through the equinox, the northern vernal equinox. If resources hold out,
if the spacecraft is healthy and funding holds out, you know, I mean
it's not just the resources on the spacecraft.

The - one of the things that's being looked at right now is whether it
would be possible to keep Cassini going in another extended mission
ideally through the solstice, which is in 2017, the northern summer
solstice, which would just give us a spectacular amount of data of the
seasonal changes in the rings and in Saturn itself and of course on
Titan.

And a great long, you know, baseline for understanding the activity on
Enceladus as well. But of course that depends on those resources holding
out and the spacecraft holding up. But that kind of - there's the
potential for that and we're certainly hoping that that would be able to
happen.

Man: A follow-up question: the New Horizon spacecraft flew by Jupiter.
Will that trajectory pass it through the Saturnian system?

Elizabeth Turtle: I do not believe so.

Man: Okay, thanks. Well thank you so much and\...

Elizabeth Turtle: You're very welcome.

Man: \...amazing - just amazing.

Elizabeth Turtle: It's been an exciting year.

Man: Yeah, when you think you're looking at things a billion miles away
it's just amazing. Thanks.

Amanda Hendrix: More questions out there? Okay, well with that then I
think that I will give one final thank you to Dr. Turtle and Dr.
Alexander. Thanks so much for putting together the presentations and
taking the time to tell us all about your work. We really appreciate it.
And thank you all for calling in.

Elizabeth Turtle: Yeah.

Jane Jones: Amanda, stay on for just one second. I need to ask you a
question.

Amanda Hendrix: Okay. And I want to remind everybody that the CHARM
presentation that we have in a month, which will be the last Tuesday of
August, what will be the final segment in the fourth anniversary
segment - or whole set of telecons. And what we'll be covering there is
results from the rings discipline. And we'll also cover what is coming
in the extended mission. So stay tuned for that. And with that we'll
just thank everybody once again. Thanks for calling in everybody.

Woman: Thank you very much from California.

((Crosstalk))

Elizabeth Turtle: Okay.

Jane Jones: Thanks.

Amanda Hendrix: Bye, bye.

Man: Bye everyone. Bye (Anita).

(Anita): Bye.

Man: (Anita), are you still there? Ah, son of a gun.

END