**FTS-NASA-VOICE**

**November 29, 2005**

**1:00 p.m. CST**

Coordinator Good afternoon. Thank you all for holding. I just need to
inform all parties that this call is being recorded. If you do have any
objections to please disconnect.

Thank you, ma'am. You may begin.

T. Ray Welcome, everyone, to the term telecom for November. We're very
excited today to have Dr. Rosaly Lopes with us. She's got extensive
experience on Galileo and volcanoes, and she comes to us here on the
Cassini Team from the radar instrument. She's the investigations
scientist for radar. We'll be talking about the geology of Titan as see
from Cassini Radar today.

Rosaly, we have the full two hours, but of course usually with just one
speaker we go about an hour or so, but feel free to take your time. We
do have the conference line for the full two hours.

R. Lopes I might feel hungry before then. It's lunchtime here. Well,
hello, all. Should I start now?

T. Ray Yes. Go ahead.

R. Lopes So you all got the PowerPoint. I'm going to talk about the
surface of Titan, particularly geology, as seen by the Cassini radar
mapper. On this first slide I have, first of all, the names of all the
people on the team. We have a pretty large team and I hope I got
everyone in there. Our team leader is Charles Elachi, who also happens
to be the director of JPL, so he's a very busy guy. We have a globe here
where we show our first two swaths from our flybys.

So we'll just go on to the next slide now, slide two, and here I show
the swaths that we have acquired during the various flybys in which we
had the radar. Now you have been following Cassini for some time, so I
assume that you actually know that we actually divide the Titan flybys,
they are very heavily contested between instruments, and we have some
flybys for optical remote sensing, some for radio science, and some for
radar. So we only get a few of the flybys.

The great advantage of radar is that it can see through the surface, and
we're going to talk more about that later with more clarity or detail
than other instruments. However, a disadvantage is that in each orbit
you just acquire a swath, a fairly narrow swath, because you can't use
this synthetic aperture mode from very large distances. So you have to
wait until you're close to Titan to actually turn the SAR on. We have
all the modes as well that I will explain. But the first globe on the
left side shows TA, which was in October of last year, T3, which was in
February of this year, and the second globe shows the end of T3 there
and T7 where we actually had the problem with the spacecraft. Trina
could go into it in great detail, and we only acquired essentially half
the swath. The third globe shows our most recent swath acquired during
the T8 flyby, which was last October 28^th^. So this is what we have so
far.

Slide number three now, again, I assume that most of you have been
coming to these telecoms for awhile, so you know a lot about Titan
already, but just to give you some background. Titan is actually bigger
than Mercury, so it's a planet in its own right. It's a speck around
Saturn, so of course it's a satellite, but this is a substantial world.
It is one of three giant moons, essentially, Ganymede, is the largest
... in the solar system, Titan and Callisto. And it has the second
densest atmosphere of solid bodies in the solar system. Titan is the
only moon that has a substantial atmosphere; it's the only object in the
solar system apart from the Earth to have nitrogen as its main
atmospheric constituent. It also has methane. Now methane is liquid at
95 Kelvin, which is the surface temperature of Titan. So that is given
of course arise from quite some time ago that it could be liquid on the
surface of Titan.

What makes Titan so interesting is that many of the processes that we
see on Earth, for example, the geologic process, we think that they
exist on Titan, but at much lower temperatures. In fact with Cassini
radar we see that all the major geologic processes that we have on Earth
we also have on Titan. So Titan is very different from the Earth, it's
like I think someone called it "Earth in Deep Freeze," but at the same
time it's got some great similarities. It's very Earth-like in many
ways.

When I was actually going to give a talk at the University of Las Vegas
I found this quote from Space.com that Titan's surface temperature is
lower than a lounge lizard's moral character. So I thought that was
quite funny and appropriate for this seminar I was giving. So we have 44
flybys, 45 including 20 in the main Cassini mission. We are hoping to
get an extended mission, and to have more Titan flyby's in the extended
mission. Of course, in the inner team we are hoping to have much more
radar.

Now slide number four, some of Titan characteristics. Again, the dense
atmosphere, mostly nitrogen, a few percent methane, there are scientists
who are atmospheric scientists who get very excited about this
atmosphere, and say it may be like the Earth before life evolved. Now
this shows a very nice image taken by ISS with a filter centered at 338
nanometers, which is sensitive to UV light. You can see here two thin
haze layers. The outer layer is detached, it appears to float high in
the atmosphere, and because it's very thin the high haze layer is best
seen against at outer rim. So the image was taken in ultraviolet. So you
can see here that the globe of Titan appears to have this orange hue,
which is what your naked eye would see that the haze is actually colored
purple to enhance their visibility.

So the best possible observations of these detached layers are made in
UV light. This is an old image, so several of you have probably already
seen it. Now the haze is formed by ultraviolet light breaking down
methane and nitrogen molecules. These products are taught to react to
form more complex organic molecules. So this makes the chemistry of
Titan very, very interesting, all of the hydrocarbons that we think
exist there. But the haze also makes it tough for the imaging instrument
to actually see the surface. I'm going to show that better in the next
couple of slides, which is the justification of why does Cassini have a
radar. Voyager actually just saw Titan very much as an orange globe, it
did not see the surface, and that was one of the main unanswered
questions from Voyager what was down on the surface of Titan, we expect
things very interesting, but this was the reason why we put a radar on
Cassini.

So the slide number five shows actually that imaging can use a
near-infrared filter to see the surface, but it doesn't see the surface
with the kind of resolution that you can get from radar. I'll show here
in the next slide, number six, I borrowed the next two slides from
Jonathan Lunine, a colleague of mine on the radar team, and it's I think
a very nice example of how haze limits the information that you have in
an image. So you have the Chrysler Building in New York on the left on a
clear day, and on the right a picture taken by Jonathan on a hazy day.
You can do a lot of image processing, of course, and I think Jonathan
just did this with Photoshop. So if you go to the next image you see the
same tab, but now the image on the right has been enhanced. You can
actually pull out quite a bit of detail, but you still lose the
information on the distance. If you actually look at the corners in
particular you lose the shading. So even with an infrared filter and a
lot of image processing, and I do have colleagues on the imaging team
that are absolute wizards at image processing. But there is still a
limitation on what you can get out of an image.

Now the next slide, number eight, shows VIMS, we also have VIMS on
Cassini that can see down to the surface, and to be visible in an IR
spectrometer. Here is a composite of false collar images taken at
several wavelengths, and it shows very nicely the methane cloud at the
South Pole, the inset of the landing site. Again, this image has been
released for a while.

If we go to the next image, number nine, when the spacecraft gets pretty
close to the surface and VIM's is observing a close approach they can
actually see geologic detail. Unfortunately it's like postage stamp size
areas that they can get, but one of the most interesting things they
have seen is what we call the snail, and it is the subject of a paper by
Christophe Sotin and others in *"Nature"* a few months ago. This is a
structure that may be a cryovolcano, and is about 30 kilometers in
diameter. So far we haven't seen anything else quite like it, although
in Radar T8 there is something that appears to be similar. The
interpretation from the VIM's team is that this is some kind of
cryovolcanic dome. Radar has not yet imaged this area, but I think that
radar would tell you the definite answer if we actually look at this
area with our resolution.

Volcanism I'm going to talk about later on because of course it's my
favorite subject, I'm a vulcanologist. Cryovulcanism was predicted on
Titan. We have not seen any evidence of active Cryovulcanism yet, but we
have seen plenty of evidence that cryovolcanism has taken place on the
surface.

So other ways to see the surface on slide ten I'm just showing one image
from Huygens because this is just to give you some background
particularly people who may be new to this telecom. Of course with
Huygens ... the imager and spectral radiometer you can see the surface
in much higher resolution than radar can give you, but again that's just
a very, very small area on the surface. It would be great if we could
have had lots of probes, and maybe one day that will happen. But Huygens
showed channels on Titan, and on this part of Titan, and in fact we are
going to look at this area later on in the telecom with radar, and the
channels that are here you can't actually resolve in the radar, which
over that area was about 1200 meters per pixel resolution. So there may
be lots and lots of channels on the surface of Titan that even with
radar perhaps our best resolution is about 300 to 350 meters, and
perhaps we wouldn't be able to resolve.

So slide 11 gets into Cassini radar. Having given you justifications why
we put the radar on Cassini, it's mainly to look at Titan. We do do some
observations of icy satellites and Saturn and the rings, but using our
radiometry and scatterometry modes not the synthetic aperture radar. But
the radar instruments and the wavelengths is 2.17 centimeters, it
operates in four modes. Radiometry is a passive mode, and we use it
generally when we are far away from Titan and other objects.
Scatterometry is an active mode, and Steve Ostro, who is on the radar
team is our main expert on radar scatterometry. We use altimetry on
Titan and imaging. The imaging is mode is soft synthetic aperture radar.
This is the same mode that was used by Magellan on Venus. It also has
been widely used on Earth because it can penetrate the cloud haze.

But we only use the SAR mode at altitudes below about 4,000 kilometers.
We are kind of pushing that up a bit now. Spatial resolution is about
300 meters to a kilometer. What we obtain is a swath about 120 to 450
kilometers wide using five antanna beams, which I'm going to show in the
next slide.

So the coverage we can get on Titan is dependent on the spacecraft
range, and also on the geometry. So we don't have a lot of choice over
the areas where we can observe. So even if we want to observe, for
example, I'd love to take a look at the VIMS snail with radar, but
that's not proving easy to do, maybe we'll be able to do that in the
extended mission.

The next slide number 12 shows the Cassini radar and essentially how it
operates. If we look straight down, if we look nadir we get our
altimetry footprint. So far we have obtained altimetry over much shorter
let's say altimetry swaths Titan than we have thought. We have the
results of the altimetry I'm not really going to discuss today, but lets
just say that it's showing very shallow slopes, it's not showing any
mountains or any major features. But we don't have any altimetry yet
over any parts that we have SAR because if you see here in this drawing
you can't use altimetry at the same time that you use SAR. So we use
altimetry when we are a bit further out than 4,000 kilometers. We look
nadir, and then we turn the spacecraft sideways because this is a side
looking radar, and that's how you get an image. So you get the image
swath. As the mission progresses we'll be able to get altimetry over the
same parts that we get SAR. Also, if we get two SAR swath's crossing
over each other we can then do tricks with the radar image processing
essentially and actually get topography, it's a bit like using stereo
for images.

The next slide, number 13, shows again our sequence of observations, and
it's a different way of looking at it. So from 30,000 kilometers and
above we use radiometry. Down to about 10,000 kilometers we use
scatterometry and then we use altimetry, and finally we use SAR. Let's
go on to the next slide now, number 14. Here are the two initial SAR
swaths TA and T3, which are on the same hemisphere they are mapped over
the ISS, one of the earlier ISS mosaic. And as you can see ISS has not
yet imaged the northern part of Titan. So TA is really over terra
incognito and radar is the only instrument that has had a look there.

So TA we got scatterometry, radiometry, altimetry. T3 we got a longer
SAR swath because TA was actually shared with INMS, b ut we didn't get
the whole path, so we didn't get in and out scatterometry and
radiometry. In some of the correlations you can see a little bit from
this image, but generally they are correlations between what is radar
light or bright, and what is bright in imaging, but not always, because
radar is not looking at the very top surface as imaging is. We can
actually penetrate a few centimeters.

The next slide, slide number 15, shows the recent encounters. The first
was T7 that happened in September. In fact while a lot of us were in
England at the Division for Planetary Sciences meeting and we kept
getting these e-mails about how there were problems. If Trina hasn't
explained to you the problems why we only got half the swath she could
go into it at great lengths. But we lost a lot of data. Luckily we
actually got half of the SAR swath. So it was unlucky, but given what we
managed to get perhaps the fate chose it so we got the best possible
part of the data. Again, here it's plotted over imaging and the
correlations of light and dark are not quite so good for this area. Then
you see better when it's plotted over this HST globe. We do this plot
mainly to show you the radar coverage as we are acquiring them. Here in
the corner you got TA and T3 for reference.

Our last encounter, we can argue was our best one, was T8. We got the
beautiful long swath and then lots of interesting stuff. The encounter
went very, very well. So sometimes you really get lucky. That happened
on the 28^th^ of October, which also happened to be my only son's
birthday. But we were lucky because we didn't actually get the data
until the next day so I actually could spend his birthday with him.

The number 17 - a little explanation about SAR because SAR is really
what you use to see geology. So that's what I'm going to go into. Now
it's a bit tricky to do geology with SAR, and in fact I have never used
SAR before to analyze data. So it's still a bit new to me, but what
you're measuring what you're seeing are variations in surface slope,
surface roughness, and dielectric properties. So you actually have to be
careful when you interpret geology from SAR.

On Titan your likely surface materials are ice, ammonia water ice
mixtures, hydrocarbons, tholins, they are very different from those of
bodies previously imaged with blind ... radars, which are mostly Earth
and Venus. The way the radar waves are scattered may be very different
on Titan. So this is just something to tell you that we have to be
pretty careful in our interpretations of what type of geology we're
seeing with SAR. Luckily they are geologic features, which tell you
about geologic processes that they stand out really well in SAR.

Slide number 18 shows we're still actually now writing a mapping paper
using SAR. We are still in what I call ... identification of geologic
units. In TA and T3 we see eight units that we actually identified and
correlated between the swaths, we haven't finished doing that for T7 and
T8 yet, but we can map this unit based on the radar brightness
variations, the general shape, the texture, but we have to be careful
about classifying them as rock or ice, or stratographic units, and look
at what unit was laid down before what because with radar its actually
pretty complicated. We don't yet fully understand the causes of
variation in radar brightness. It could be composition, it could be
scattering effects, and it could be roughness. But as we analyze the
data more, and as we get more data and correlated the swaths we are
getting much better at this.

Now we see cryovolcanic features in the first swath TA, possibly T3 and
T8. Actually I consider myself very lucky. I was really hoping for
cryovolcanism on Titan so that I would have something to do and in the
first swath we see several features that we think are cryovolcanic.
While a colleague of mine on the team, Chuck Wood, he's an expert on
impact craters and he was hoping to study craters, we didn't see any
craters at all in the first swath. So he was getting rather worried that
there wouldn't be anything for him to do. But in T3 we found two craters
for him. So that was good.

We also find similar features in sun shaped units and all the swaths
meaning again the fluid transport of material. We find that coastline in
T7, which is a candidate for liquid and I'm going to show you all those.
Two impact craters in T3, these features that we call cat scratches,
which we interpret as dunes in T3 and T8 and possibly tectonic features
in T8. So the variety of geologic processes is just incredible. In fact,
I'm going to back track now a bit just to say that when you look at
solid surfaces of planets every solid surface of every planet is an
interplay of four major geologic processes. You have the endogenic
processes, which are volcanism and tectonism, and the exogenic
processes, which are impact cratering, and erosion. How the surface of a
planet will look depends on which processes existed and were dominant at
particular times. So, for example on Earth, we don't see many impact
craters because we have had plate tectonics destroying features and we
have a lot of erosion. On the moon we still see a lot of impact craters.
So it's really the interplay of the processes that determines what the
surface of a planet will look like. Titan looks like it's got all of
them. So this is really exciting for us to unravel the geologic history
of Titan . We have to unravel how these processes fit together, and at
what particular times.

So let's go to 19, this part of the TA swath, and show that in our first
swath we see a remarkable diversity of features, including several
flow-like features. So if we look at the top swath we have the round
feature, which is called Ganesa Macula, we're going to get in more
detail, we think that's a cryovolcanic dome. We have a number of flow
features to the right, including some like deltas, which may be
cryovolcanic, or they may be alluvial, but, again, indicate the
transport of material. To the right of that some sort of fairly smooth,
or what appears smooth, homogeneous plain, but with some darker patches.
There is an arrow type feature on the top part on the right hand side of
the swath, it actually looks like it could be some type of tectonic
feature because of these straight lines. If we go to the bottom swath,
right in the middle of what we call nickname the Cece the Halloween Cat,
and there is radar dark area - dark in radar normally means smooth, and
we think this might be candidates for surface liquids.

One of my colleagues calls these a cryoswamp, so maybe we have not
oceans on Titan, and maybe not many lakes, but we might have sort of
swampy areas of these interconnecting ponds. On the far right of the
second swath a really big flow that we think is a really big
cryovolcanic flow. So right in the first data we got we see this great
variety of geologic features.

Then slide 20 just an example of how we actually tried to map features
and classify them. Here homogeneous units, or the age that these sort of
darkish units that appear to be homogeneous, and possibly ice plains.
Then other areas, the bright area at the bottom, is actually the toe of
that big flow that appear rougher and definitely different.

If we go to the next one, some other examples. Here we see where we drew
a boundary, although it's not very well defined one, between the
homogeneous unit and what we call the mottled unit, which appears to
have this bright small scale features, but we're not quite sure what
these features are. But we know it's a different kind of region. We see
the same type of feature in the T3 swath but it's actually brighter and
more extensive. So part of our work now is to actually correlate these
various units in the different swaths.

Slide 22 shows again a different type of unit, and that's what we call a
hummocky unit, and you can see that it is much rougher and it might be
small hills. It's very much more textured and it appears to be embayed
by the surrounding plains. That means its possibly older than the
surrounding plains, but one of the things we have to figure out in
geologic mapping, if we can, is what came first and what came second
because that's how you reconstruct the geologic history of a surface.

These hummocky units occurs in both TA and T3, and I'm not going to go
through all of the different units now, but this just gives you an idea
of how we do mapping of the different features that we see on different
swaths.

Slide 23 is the dark mottled unit, Cece the Halloween Cat. Here we call
it DM, or the Dark Mottled unit. On the figure on the right you can
actually see some sort of ox bow shapes that could be liquids. So I
don't like to say guess, but we think that these areas may be surface
liquids. They're certainly candidate areas for surface liquids, but we
can't prove it. In fact it's turning out to be a very difficult thing to
do to actually prove that any features, even the lake that ISS sees, is
actually liquid. So there's still a lot of observations and a lot of
work to do.

The next slide 24 the features that are actually easier to identify and
identify what they are, features such as the flows, the fans, and the
deltas that we actually can see from the morphology pretty much get an
indication of what process formed them. There's two fine light features.
They are much larger in scale then the Huygens channels, but they could
be essentially narrow channels, that's what we think they are, narrow
channels will open out into this fine light deposits probably because of
a change in topography.

What this is indicating is transport and the disposition of materials.
So erosion is happening on Titan. What is the process exactly that's
transporting the material? Well it could be a kind of river type
process, or it could be cryovolcanic. This is not yet possible to sort
out which one it is. But it's definitely evidence of liquids that have
been transported on the surface, have flowed on the surface, and there
is also evidence of some topography because narrow channels actually
open out into this big flow, and it would be great if we could get some
altimetry or some cross over swaths over this area to actually tell us
this topography.

In T3, the next slide number 25, we got more evidence of these channels,
a very nice deposit here that we think is definitely alluvial. Ralph
Lorenz from Arizona is writing a paper on these features at the moment,
and we see channels that are actually draining, actually flowing from
the bottom to the top, and draining into a depositional area. These
dendritic braided meandering channels are very characteristic of river
channels on Earth that split up and regroup and so on. There is not a
lobate deposit here. So we don't think this is cryovolcanic, we think
that this is much more likely to be alluvial.

The next T7 slide 26 that shows our famous T7 coastline, and this is one
of the best pieces of evidence we have for surface liquids in the past
or the present. I think two most clear indicators that we have seen are
the ISS lake, which probably most of you have seen, and this feature,
the coastline. So here you see on the left hand side, a bright rough
region that appears to be topographically higher. It's cut by channels
and bays, and then this boundary, which we think is a shoreline, and
when tinted dark there are patterns that don't show up very well here,
but that indicate a flow. The big question is is this liquid now, or was
this liquid in the past. We can't answer that yet. But at least we have
the indication that there have been areas such as lakes or big lakes in
the past.

The next slide shows here a comparison of T7 - is our most clear
coastline feature. T8 our recent data there are these dark patches that
perhaps could be an older coastline, but most of us are still not very
convinced by this. There may be a lot of areas on Titan that were liquid
in the past and are not now, but you still see some evidence of them. It
is one of the big questions that perhaps for our next mission to sort
out, this how much liquid actually exists now on the surface.

So our next slide - 28, our big class of features are impact craters -
and these are the two impact craters that we have seen, and they are the
only two impact craters clearly seen on Titan so far. The top one is
actually a basin, it's a pretty big crater, about 450 kilometers across,
it has an outer and an inner ring, you can see the rings are bright, and
this is a characteristic of basins. You see basins on the moon and
Mercury with concentric rings. We only see parts of it in our swath, but
it is evidence of a very large impact.

The crater has been named Menrva, it's apparently pronounced the same
way that Minerva is pronounced from Roman Mythology. The second crater,
a smaller crater, 80 kilometers across, looks more like your
characteristic impact crater with a big ejecta blanket that's been named
Sinlap. Both of these are sages of wisdom. Menrva is Etruscan \[The
Etruscan version of the Greek Athena\] and I should know but I forget
where Sinlap is from.\[Kachin (N. Burma) wise spirit who dwells in the
sky and gives wisdom to his worshippers\] In fact recently I joined the
nomenclature group for the International Astronomical Union, the task
group for outer planets. So I'm now helping decide on these names. I
think I would have picked another name than this funny spelled Minerva
that none of us is quite how to pronounce. But going back to the
craters, so those are the only two clear indications of impacts that we
have seen on the surface, ISS had seen circular features that might be
impact, but we haven't had definite evidence yet.

The basin actually the left side of the basin appears to be much more
eroded than the right side, and I'm going to show a picture in more
detail later, but you can see here at the bottom some channels. So there
is evidence that this is pretty old and has been eroded. Now Titan,
because it has an atmosphere it does provide some protection of the
surface against the smaller meteorites, like similar to what the Earth
does. On Titan you need impactors greater than about two kilometers in
diameter, which would form a creator about 20 kilometers in diameter. So
you don't expect to see lots of small craters on Titan. But what's been
surprising is that at least compared to the impacts on other satellites
of Saturn, we have seen far less on Titan than we had expected.

The next slide, slide 29, shows a nice comparison between radar and
VIMS, this is a way to show the Sinlap crater, and this is a way of
putting together data from different instruments and really help to
understand the particular features. We have VIMS at 2.03 microns, which
is one of their methane windows. Then the radar T3 in a VIMS false color
made from three different wavelengths. The VIMS actually if you compare
the images you see the extent of the impact ejecta around the crater is
different. On the false color of VIMS you see that it has a faint halo
that is shown here is bluer than the central bright material. This is
implying a different composition of perhaps grain size.

As an impact excavated the deep layers of the surface what happens
during an impact is the top layers will be ejected and land closer to
the crater, and then the layers that are excavated as you go deeper as
the shock from the impact excavates those layers, those will end up on
top and on the outer edges.

J. Howler What is causing the break in the swath in T3?

R. Lopes That's a data gap.

J. Howler Why does it come in square blocks if the image is with a
circular disc wouldn't they have a circular section to it?

R. Lopes Interesting question. I never thought about that. I think it's
because the radar beams are actually pretty small compared to what you
see here. So it's a gap in time. Probably also radar engineers didn't
use pieces of data so they cut it there. But, frankly, I don't know
exactly the answer to why it looks square. I never thought about that.

J. Howler Do you know why there was the data loss to begin with?

R. Lopes I can't actually remember. I think it was a DSN problem. Trina,
do you remember?

T. Ray This was the transition from one way to two way. We have a small
dropout that occurs when the spacecraft transitions from coherent to
non-coherent, and this time it was radar that took the hit.

R. Lopes It's still possible that it might happen.

T. Ray It happens in every down link. It's a gap of about two minutes,
and it happens in every down link that we have in a mission. We decided
we wouldn't do anything about it. But then after seeing this we said,
"Well that's not maybe the best answer," and protect for targeted flybys
and protect ourselves from this. So now we protect ourselves from this
kind of outages.

J. Jones Can the speaker identify themselves for the transcript?

J. Howler My name is John Howler and I'm calling from Menlo Park. Thank
you for your comments.

R. Lopes Actually if you send me an e-mail I'll find out the answer
about the squares. You're right because our beams are circular. But it's
something I never noticed before. So thanks for bringing it to my
attention.

So I think we can move on from this. But this is a comparison, again,
showing how easy it is to put the various instruments together.
Something else that you can see here is the center of the crater is dark
in the VIMS 2.03 microns and you actually think that the ejecta is
pretty different because it's light on VIMS, while on radar it's about
the same, and radar is showing essentially here I think is that the
roughness is similar while the VIMS is showing the IR properties. Also
the depth that these different instruments sample is different, radar is
actually sampling a few centimeters deep, while the VIMS is just seeing
the very, very thin top layer.

The next slide, number 30, the famous cat scratch is some of our
favorite features, which we think are dunes. Now we first saw these in
T3, they're not present at all in TA, in the first swath, they are all
over in T3, and we just looked at them and thought, "Wow, what are
those?" We thought of tectonic features, but they really don't look like
tectonic features, and we thought of fluid flow, and eventually the best
explanation we came up with is that they are longitudinal dunes. Here is
a picture from the Arabian Peninsula so this happened a lot on Earth and
now that we are looking for more of them we find a lot of these in dunes
in Namibia and other places. So they form along the direction of wind.

In TA we see some areas where there might be some very faint ones, but
it's the kind of case that if you think something is there than you can
go back to the data and try to see it, but we're not convinced yet. But
they are all over in T3 and T8. T3 and T8 are more equatorial swaths, so
we think that actually there is a control where the winds are stronger
in the equatorial regions. The next slide shows a close-up of the side
of that impact basin, Menrva, and it shows here the channels at the
bottom, and it shows the patches of what we call cat scratch patches.
These do look actually like the claws of a cat, and that's why we
nicknamed them cat scratches because that's what they look like before
we actually started interpreting them as dunes. In some places they are
truncated, pretty abruptly, in other places they sort of fade away. They
are dark in radar, and they are also dark at optical wavelengths. We are
trying to correlate now radar and VIMS. So far we're working with
members of the VIMS team. We have not found a difference in composition
between the cat scratch patches and the other areas.

But if they are dunes you wouldn't really expect to see a difference in
composition, it's just material moved around. Now in T8, they next slide
32, we see them in a lot more detail and can really put them in context.
There is a paper by Ralph Lorenz that's actually being submitted in the
next few days to *"Nature*"*,* and where we actually argue really that
these are dunes. You can see on the bottom image here how nicely this
dune features go around what appears to be a topographic high. So
they're like diverted, and you see these on dunes on Earth, and T8 has
really been a revelation for the cat scratches - they really look much
more like dunes now.

T8 also showed us, in the next slide, some features that appeared to be
tectonic. These apart from the small arrow type feature that I showed
you in TA, we had not seen conclusive evidence of tectonic, but we now
see a lot of linear features that really may be like ridges. Now
tectonism is not the only explanation, we could even have a
cryovolcanism along fractures. But we don't exactly know what these are
yet, but long linear features appear like some tectonic process has
taken place.

Here you see a number of cat scratches as well, particularly on the
right hand side. The T8 swath has just got a lot of them. But the big
excitement of T8 in the next swath is actually the radar was able to
observe the Huygen's landing site. The reason we wanted to do that was
to provide contacts for the Huygen landing site, and is off to find out,
"We see all of these channels and things in the Huygen images, now what
do they look like in radar?" In fact you don't see those in radar, it
was actually pretty difficult to even match the DISR landing site of the
radar.

Now this is a good estimate, it's not the best one. Unfortunately,
there's a press release tomorrow, and I can show you the latest yet. But
if you look in the Cassini Web site in the next couple of days, there's
an ESA press conference tomorrow in Europe, and the stuff should be
released on the Web site in the next couple of days. But we had a couple
of people in our team, particularly Larry Soderblom and Jonathan Lunine
actually spending quite a bit of time trying to match the radar with
Huygens. Now one difficulty is that this is pretty low resolution SAR.
We in fact we extended the SAR swath beyond what we would normally get
to be able to get the Huygen landing site. So this is like 1200 meter
resolution, while a closest approach we normally have about 300 to 350
meters. It does make a big difference what you can see in terms of
geology. In fact, Jonathan Lunine just sent me today some terrestrial
radar images of Italy. He actually degraded the resolution, and showed
it at 350 meters and 1200, and the difference in what you can see in the
geology is just amazing.

So this is not the best possible radar data we can get over the landing
site, and we hope to have other opportunities in the future. So I hope
that you look for the press releases in the Website in the next couple
of days. Something that I can actually give you this hint is if you look
at the panorama image that was obtained by DISR, and I'm not quite sure
exactly where in the Web site it is, but it was taken closer to landing
and shows a beautiful panorama. You can actually see in the distance
some cat scratches that only now that we know that we are we actually
can correlate them with cat scratches, but it's really pretty amazing.

The next slide, now I'm getting on to what I really like to talk about
because it's getting to the end of the telecom, Ganesa Macula. Well I
like cryovolcanism, and so I'm going to spend a little bit of time on my
favorite subject. Macula, by the way, is just a name given to a dark
feature, usually in the nomenclature committee and unless interpretation
of a feature is really clear, we try not to sort of make geologic
interpretations. So names like Macula are useful because you can say,
"It's a dark feature so we call it a Macula." Bright feature you call it
a Facula. We're pretty sure this is now a cryovolcanic dome, but at the
time it was named it was still being cautious. It's about 180 kilometers
across so it's pretty large compared to a lot of the pancake domes on
Venus, which we also show here at the bottom. These are two pancake
domes on Venus, and we think that's what the Ganesa Macula is.

A pancake dome is a steep sided dome, and is essentially formed by the
extrusion of magma or cryomagma that's quite viscous, and relatively low
in gas compound so it's not explosive. Like the Venus domes this has a
central depression. Ganesa also has some channels that may be cryolava
channels or they may have been formed later. We are still working on the
interpretation and the number of flow features to the right of it. The
little image here, Ganesa, is the Hindu God of Good Fortune and my
colleague, Randy Kirk, found this image.

The next slide the predictions for Titan's geology, pre-Cassini included
cryovolcanism. Well cryovolcanism is cold volcanism so it's not magma
and it's not molten rock, it's water or more likely a mixture of water
and other constituents such as ammonia. Now ammonia water mixtures are
consistent with compositional models of Titan, and ammonia lowers the
melting point, the density and the mobility of liquid water. So it's
actually easier to erupt an ammonia water mixture than it would be to
erupt pure water. Ice cubes float, so that gives you the idea you
actually need some other process to actually get this liquid water to
the surface. The interesting thing about the ammonia water mixture is
there was a lot of work done by Jeff Cargill from the University of
Arizona in the early 90's about the rheology and the viscosity of these
mixtures. In fact they can produce features very similar to what you
would get on Earth with basaltic and other magmas because ammonia water
actually has a high viscosity.

Another projection by my colleague Ralph Lorenz was that the cryomagmas
would probably have relatively low amount of methane, which would be the
main volatile and not enough of Titan's atmospheric pressure to produce
explosive eruptions. In fact we don't actually see any features that
look like the features caused by explosive eruptions such as steep sided
cones. Ralph actually predicted that pancake domes might be the most
likely volcanic landform, and we see flows, and we see a pancake dome,
so it was a good prediction.

The next slide shows you just a closer up of Ganesa Macula and some
comparison with a variety of Venus domes. So that's what we think it is.
Now go on to the next slide 38 we also see these very long flows. On the
right hand side you see a crater with a flow coming out of it. Now
people can argue if you see long flows on the surface like the biggest
ones, this est ones, how do you know if it's cryovolcanic, it might be
alluvial. But when you see a crater with a flow coming out of it it's
pretty difficult to do that with anything else than vulcanism.

> We see in TA there is another crater with a flow coming out of it, and
> together with Ganesa Macula and so on we're pretty convinced that
> cryovolcanism has been a major process on Titan. But the origin of
> particular flows such as this large bright flow you could still argue
> a bit even though to do it from rainfall it might take an unreasonable
> amount of rainfall.
>
> In the next figure, slide 39, I actually show this big flow on this
> lobate shape and actually seems to be coming out of a series of
> fissures, and unfortunately our swath cuts of there, so we don't
> actually see much of the source. It might be similar to what you see
> on the lower distant image on the right of Mauna Loa taken from CIRC
> radar, and it actually shows here a rift zone with a number of flows
> coming out of it. So it might be something similar to that.
>
> The next slide, number 40, it's more about how you tell a cryovolcanic
> feature. An association with a vent - is really the key sign that you
> look for - a crater, a caldera, a fissure - they form constructs such
> as domes and shields, lobate deposits, and going into cryolavas a bit
> they are erupted at much lower temperatures than silicate lavas, they
> can resurface vast areas, and they can form this land form similar to
> what you see on Earth such as shields and domes. The composition is
> something we're trying to get at now because the composition of these
> cryolavas has a large effect on the viscosity. Ammonia water has
> rheaologic properties similar to silicate lavas, so you would see that
> in the flow thickness, you would expect some well defined thick
> margins that you see in some of these flows. A final morphology such
> as a pancake dome, and I have a post-doc here at JPL Cal Mitchell
> who's actually modeling and may start doing some laboratory work with
> these mixtures. Something we are finding is that perhaps water ammonia
> is not actually enough. Some of these flows appear to be of very high
> viscosity and maybe there is something else like methanol involved in
> these mixtures.
>
> But something that is interesting is that it's very hard to get the
> composition of these lavas by other means. For example, VIMS has not
> detected any ammonia on the surface at all, and the depth that VIMS
> sees actually may not see any ammonia because they have a layer of ice
> at the surface so that's all you see. So this rheological measurement,
> this thickness measurements that, for example, if you have a channel
> and a thickness of a channel margin, you can use models for further
> viscosity. This may actually be our only way at the moment of getting
> at the composition is to actually do this rheological analysis and
> look at the final morphology of the deposit, do modeling experiments
> to actually try to see what the composition of that cryolava was.
>
> Now that we see cryolava's anywhere else than TA, well T8 we have some
> features that might be calderas. T3 here I show on slide 41, there are
> at the top and in the middle there is a feature that I actually call
> them the little comet, and this could be a crater with a flow, and
> unfortunately the resolution is not good enough to tell. We still
> discussing T8 whether there are some features that they appear to be
> like calderas and they might be or might not. But the first flyby was
> the one that really showed us conclusive evidence of cryovolcanism.
>
> Finally, on slide 42, shows a location map for the recent, actually
> not upcoming, but the recent flybys. So it's just another way of
> seeing it. Slide 43 shows a planning map of the coverage during the
> mission. So we actually are going to have some of this crossover of
> swaths, which I think are really important because we can get
> topography from this crossover swath. If we actually really need the
> topography we'll be able to much better constrain the geology of these
> features.
>
> Slide 44 in conclusion, the surface we have seen is a very young, I
> forgot to update this number, but we've seen over 4% now . It is a
> dynamic surface. We see some smooth areas that may be liquids, but we
> can't tell yet. We see a variety of geologic processes, cryovolcanism,
> fluid flow, these channels, and erosion deposition. A couple of impact
> craters, aeolian processes, and the cat scratches and dunes, and
> probably some tectonics. So it's, again, the wide range of geologic
> processes and how they interplay with one another, and how the surface
> of Titan really evolved. It is going to be the subject for study for a
> long time.
>
> So thank you very much. If you have questions I'll be pleased to
> answer.

T. Ray Usually we have questions. So, Rosaly, what's something that
you're looking forward to in the upcoming radar activities?

R. Lopes More and more SAR. I'm actually looking forward to some more of
these high latitude passes maybe at the same latitudes as TA, just
because they might show more cryovolcanic features, and this is just the
gut instinct. But because we see so many cat scratches and aeolian
deposition in the closer to equatorial regions they may be masking some
of the cryovolcanic features if they are older. So perhaps at high
latitudes we have a better chance of seeing more.

I'm also looking forward to some of these crossover swaths. For example,
if we get to 20 because that would enable us to actually get topography
by using the two different looks. So it's like a radar stereo. But I
think that everywhere we have looked is interesting. Even down to the
end of the Nominal mission we only have about 20% of the surface and
everything is going to be interesting. There is always going to be
something new. Every swath so far has looked somewhat different from the
previous ones, and we see new things.

J. Vitello This is John Vitello from Park Ridge. Are there are pancake
domes on Earth? Also, could you describe how a pancake dome is created
and the difference between a more pyramid shaped volcano?

R. Lopes It's a matter of composition. I'm going to use lava as general,
or maybe cryolava. But what you need to form domes is essentially high
viscosity and low gas content so that you don't get explosions. We see a
variety of domes on Earth such as Lassen Peak, but that's more of a
pyramid type dome. The Mount St. Helens dome is sort of lower and it's
not quite pancakeish, but it's more getting there. In fact at least it
used to be and I can't remember if the latest eruptions actually have
modified the shapes some, but Mount St. Helens used to be closer to a
pancake dome.

You need slow extrusion as well. So you get this slow extrusion of lava
and then the high pressures on Venus help flatten it, but it's a matter
of low gas content, high viscosity and generally they are very slow
extrusions. Now it's a good question I can't think of any dome on Earth
that has been called by vulcanologist as a pancake dome. That is
actually a term very much used for Venus. I should say here that we
don't have clear evidence that the Ganesa actually has steep sides like
the domes on Venus. But we know that the south side, which was facing
the radar, is bright. So that indicates a slope. But it could be more
similar to the Mount St. Helens dome for example. The top appears to be
pretty uniform so that might be evidence again that's kind of flat.

I really would love another look with either altimetry or a crossover
pass over that region.

J. Howler This is John Howler again, and I have a question about finding
liquid on the surface. Do you know the temperature of the surface so you
can know the likelihood of water actually being able to be there? You
mentioned that if it mixes with ammonia than it could have a lower
boiling point.

R. Lopes They are two different things. But, anyway, finish asking your
question.

J. Howler Also, have you done any statistical analysis to determine the
likelihood of the dark patches that you have seen, is that actually a
formed or actually liquid, and can you give a percentile probability
that it is?

R. Lopes I don't actually know that you could do a statistical analysis.
I'm not sure what you would use to actually say whether it's liquid or
not. The liquid wouldn't be water, you could have water ammonia for
short periods of time if it was an eruption before it froze. But the
liquid on the surface, particularly if it's a pond or a lake is methane,
likely to be methane or ethane because of the surface temperature of
Titan. So it wouldn't be water and the mixture such as water ammonia
would only flow like over short periods of time.

It's really a big question we have on Cassini right now is how do we
actually tell that even these candidate areas are liquid. You might be
able to tell with a radar altimetry, and like how smooth the area really
is. The best chance you have is actually to use optical instruments and
try to see glints at the surface, but if these areas are small you
actually need particular geometry observations to be able to see these
glints from the surface.

Trina, you might actually know when we are doing observations like that
with the ORS \[Optical Remote Sensing\] instruments?

T. Ray I do not. I should.

R. Lopes The best evidence we have for liquids on Titan is from ground
based observations. Done with radar but at different wavelengths than
the Cassini radar. So the liquids also might be sub-surface, and it
could be the optical instruments would then never be able to see them.
Maybe we'll actually have to go there and sample it to be able to tell
if it's presently a liquid or not, or with a Titan orbiter we'll
probably get enough observations that you could do it.

T. Ray Titan Rovers.

R. Lopes That's right. Then if the rover's sink you know it's liquid.

E. Kyle It's Earl Kyle from Manchester, New York. When you're in radar
altimeter mode what's the resolution in terms of resolving differences
of height?

R. Lopes It's a few meters. It sort of depends where you're looking. I
can't e-mail any picture to you. But one of the problems with altimetry
is that we get very, very short areas that we look at with altimetry.
They're typically very short paths, and if you don't actually have the
context, like you haven't seen the area with SAR, it's difficult to
figure out what you're actually looking at. There is - where I'm going
to point you out to a paper that we published, in fact all of you might
be interested in this, in science is on the 13^th^ of May in the year
2005 volume 308. It is by Elachi et al and that's a team paper on the
results of the TA flyby. We have several other papers in the works, but
the others haven't been published yet. That actually has an altimetry
track and you can actually see the errors and the elevation.

So far what we have found is just very shallow slopes. It doesn't mean
that there couldn't be mountains on Titan, but we haven't seen them. The
widths of the beam is pretty large, for TA it's about 25 kilometers, a
horizontal resolution. So altimetry is good but it has its limitations
particularly when you're trying to do the detailed geology.

T. Ray Do we have any other questions?

Ken This is Ken in North Carolina. I've got a question about slide 28.
It has to do with the Sinlap crater in the T3 SAR image. There's a bunch
of what looked like ghost craters in that image. What are those?

R. Lopes We wish we knew. We talked about ghost craters a lot. They
could be ghost craters. But if you look at the next slide in VIMS, maybe
VIMS doesn't quite have the resolution, but you see perhaps slightly
different types of ghost craters. So there are lots of features like
that that you almost see with radar and may discuss it in the team, but
we can't really say with any certainty what they are, but we do wonder
about them. So we had some discussions on the possible ghost craters.

A. Smeticamp This is Ang Smeticamp from Penn State. I have a question
about the cryovolcanism. Would you say that perhaps it is maybe you
can't tell when the cryovolcanism occurred, maybe since three billion
years ago, but you can't tell if it's very, very recent. You said it's
relatively young surface, but what do you mean by that?

R. Lopes What we mean is that there aren't many impact craters, at least
we have only seen two. We see far fewer impact craters than you would
expect, let's say just comparing it with the other Saturnian satellites,
even taking into account the fact that the atmosphere of Titan is
actually screening out a lot of the impact of the smaller ones. But we
don't see as many bigger craters as you would expect if Titan had a
similar surface age of some of the other satellites.

So what that's telling you is that since most of the impactors were
around early in the history of the solar system is that something is
happening, other processes are going on, that are resurfacing and
they're raising those impact craters.

Something else that could be happening on Titan is the ground itself, if
it's sort of mushy it's not going to retain the craters very well, and
that's a possibility as well. So the fact that the surface is young
that's kind of a relative term compared to the other satellite. We can't
do any statistics yet because as my colleague Chuck Wood likes to say,
"You can't do statistics with two craters, and I need at least three"
Maybe when we find a few more craters we'll have a much better idea.

A. Smeticamp Thank you.

R. Lopes Is everybody getting hungry yet? I don't know what time it is
where you are.

T. Ray It sounds like we're done with the questions. Rosaly, I'd like to
thank you very much today we really appreciate you taking the time out
to talk to us about the radar results. It was very exciting. I'd like to
wish everybody to have happy holidays and we'll be reconvening the CHARM
telecom in 2006. The next one will be January 31^st^, the last Tuesday
of January, and we'll be talking about the dust results so far in the
mission from the dust detector.

M This has been fascinating. Thanks for all of your efforts. Much
appreciated.

R. Lopes You're most welcome. We enjoy doing it. Goodbye.