**FTS - NASA**

**February 22, 2005**

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

Coordinator Today's call is being recorded. Thank you, you may begin.

Trina Thank you. Welcome to the ... telecom for February of 2005. We've
been having some really exciting, exciting science being done with the
spacecraft in the last month or two. Today, we have Dr. Jonathan Lunine
joining us, he's an interdisciplinary scientist from the University of
Arizona, and a Titan specialist. So very exciting stuff. Thank you for
joining us, Jonathan.

Jonathan My pleasure. If you can manage to interrupt telecom style,
that's fine. I'll answer any questions. I suppose the protocol is I
prompt you to flip your slides, right?

Trina That would be terrific.

Jonathan Okay, first slide is First Views of an Alien World. I'd like to
get a sense of what the big questions are for Titan, particularly with
the respect to the surface of Titan and what we've learned from
Cassini-Huygen, not just from the spectacular images of the surface
which have wowed everybody, but also by mapping the surface,
particularly at radio wavelengths with the radar. I'll explain how that
works and show you some examples of radar data, some of which we've
received Tuesday night/Wednesday morning, just a week ago, so we're
still analyzing that and there's a lot more to come.

Why don't we move forward to the slide titled Titan \<gap\> This is just
a reminder of what Titan is. We probably don't need to know this, but it
is \<gap\> Saturn, it's the second largest moon in the solar system, the
biggest is Jupiter's moon Ganymede, and Titan is just slightly bigger
than Jupiter's moon Callisto, as well.

What's interesting about Titan from that point of view is it's actually
one of a triad of giant moons. I mentioned the other two, Ganymede and
Callisto. All three of these are almost the same size and mass, so if
you express the mass and size in terms of the density, the mass divided
by the volume, you come out with a number between 1.8 and 1.9 grams per
cubic centimeter. That number is roughly halfway between water ice and
rock. In fact, the most abundant element we know of in the solar system
besides hydrogen and helium are oxygen, silicon and so one so with that
bulk density, we'd say each of these three objects is about half rock
and half ice by mass. So these are icy worlds, but not as icy as some of
the smaller moons of Saturn, like Iapetus, for example. They're a bit
less rocky than Pluto and Triton, which have densities somewhere about
two. But they're definitely very ice rich.

We expect each of these bodies to primarily have the ice in a mass hole
surrounding a rock core because the rock, being denser than the ice, is
going to tend to sink, particularly if they're sources of heating. I'll
show an example of an internal structure for Titan in a few minutes.

With striking about these bodies is the close correspondence. They
really are almost identical to each other, and that suggests there is
some process that leads to the formation of satellites of this size, and
it's difficult to go much further. It may have something to do with the
fact that by the time you get to the size of Ganymede, Callisto or
Titan, as you add more materials to these bodies as they formed early in
the history of the solar system, the amount of heat that's released as
more material is added is just about the amount required to vaporize the
ice itself.

So these bodies have reached a threshold where it's possible to continue
accreting rock, but it's not possible to continue accreting ice, and
that slows the process of growth down dramatically and that may be a
natural termination point for satellites made of rock and ice.

What distinguishes Titan from Ganymede and Callisto, and for that
matter, every other natural satellite in the solar system, is that it
has a very dense atmosphere. In fact, it's the second densest atmosphere
in the solar system. It's composition was determined by voyager. It's
the nitrogen methane atmosphere, the atmosphere is predominantly
nitrogen with methane being the secondary component, and in terms of how
this atmosphere fits in with that of other bodies in the solar system,
if we leave aside the giant planets which themselves are really
self-gravitating balls of gas, mostly hydrogen and helium, we're left
with four bodies in the solar system that have substantial atmospheres.

Just to make sure everyone is still listening, can someone volunteer to
name those four bodies?

W Earth.

Jonathan That's one.

M Venus.

Jonathan That's another.

M Titan.

Jonathan Titan is another. Titan is so interesting, we've forgotten the
red planet, Mars. That's the fourth. Although it barely qualifies, it's
kind of a thin atmosphere. If you take those four bodies and arrange
them in order of decreasing atmosphere density, Venus is first, Titan is
second, Earth is third and Mars is a distant fourth. Titan's atmosphere
at its surface is four times denser than the air at sea level on the
earth. So it's a remarkably dense atmosphere.

> One of the key questions is how did it get that way. It's a stable
> atmosphere, even though Titan is a relatively low gravity body, has
> the gravity of the Earth's moon, 1/6G. That atmosphere is stable
> because the temperatures are so low. It's ten times further from the
> sun than Earth, so it gets 1% the amount of sunlight as Earth. That
> tends to allow these molecules to be retained for billions of years.
>
> The surface pressure and temperature were measured by Voyager, they've
> been by ... 1.5 bars and that should read 94 Kelvin, which is nearly
> minus 180 Celsius. It's almost minus 300 Fahrenheit. It's an extremely
> cold surface. But it has actually warmed about 10-degrees by a modest
> green house effect, which is supplied primarily by the methane,
> somewhat by the nitrogen and a bit by hydrogen, which comes off of the
> methane. I'll talk about that in a minute.
>
> I mentioned the methane is the second most abundant component in the
> atmosphere. Voyager set a range of possible methane \<gap\> to the
> surface between 2% and 10%. The Huygen's results are looking like it's
> between 5% and 10%, and we're hoping to refine that further. Then,
> because the temperature in Titan's atmosphere drops off as you go
> higher, just as in Earth's atmosphere, by the time you get up to about
> 40 or 50 kilometers, the temperature is not 95 Kelvin, it's 70 Kelvin.
> Methane will condense out, given the amount that's in the lower
> atmosphere, methane will condense out as clouds until you reach that
> temperature minimum, at which point you can only have 1.5% to 2%
> methane in the atmosphere, give the pressure and temperature of 70
> Kelvin.
>
> Methane is playing very much the role that water plays in the
> atmosphere of the Earth in the sense that, as the temperature drops,
> methane condenses out, forms clouds, liquid clouds closer to the
> surface, solid clouds, ice particles higher up. The temperature
> continues to drop to about 40 kilometers and then turns around, and is
> then in a region where the methane is destroyed by chemistry.
>
> So Titan is intrinsically and interesting and complex world. We want
> to know how complex it so it's the target not only of the successful
> Hoygen's probe mission but of at least 45 close flybys by the
> Cassini's orbiter. Let's go to the next slide.
>
> Slide three is entitled The Three Great Questions. These are my three
> great questions. Other people may have other great questions, but I
> like these about Titan. Number one, Why does it have an atmosphere?
> Ganymede and Callisto and just as large but they don't have
> atmospheres.
>
> Number two, how much methane is there really on Titan? As we'll talk
> about in the next slide, methane is destroyed quickly in the upper
> atmosphere. In fact, early in the history of the earth, there may have
> been a lot of methane as well, but was quickly destroyed by
> ultraviolet light. In the case of the Earth, methane is re-supplied by
> organisms, by biology. We don't think that's happening on very, very
> cold Titan. There are no cows to product methane on Titan. So the
> methane is coming from \... sources, the question is, what are those
> sources, how much methane is present today and how much has been there
> in the surface and in the atmosphere of Titan over its history. That's
> a key question to understanding the nature of Titan, its surface
> features and chemistry. Those are two questions that Cassini-Huygens
> are instrumented to address.
>
> The third question that goes beyond Cassini-Huygen is the question of
> organic chemistry on the surface of Titan, how far has organic
> chemistry gone on the surface of Titan. We'll see in just in minute,
> methane produces lots of interesting products, hydrocarbon, nitrides,
> these fall to the surface and the question then is does other
> chemistry occur and what are the energy sources. Cassini-Huygen have
> told us a bit about this, but it's going to require another mission to
> probe this fully.
>
> The next slide is a series of little molecules. This is a very cursory
> attempt at explaining the chemistry that goes on in Titan's
> stratosphere. Don't think about the lower atmosphere, take your mind
> up 100 kilometers, 60 miles, at least, above the surface of Titan.
> Titan's atmosphere is very extended. If you went 60 miles about the
> Earth, you'd be in space, but Titan's atmosphere, because of the low
> gravity, is two or three times more extended than the Earth's. So at
> 60 miles above the surface, there is still plenty of gas and methane
> available, but it's getting thin enough that, above that, there is not
> enough gas to prevent ultraviolet light from the sun from penetrating
> through. And ultraviolet light from the sun is that higher energy,
> shorter wavelength light that's capable of breaking up molecules.
>
> If you look on the left of the slide, you see methane. The dark gray
> balls are supposed to be carbon, the light gray smaller ones are
> supposed to by hydrogen. So methane is the simplest organic molecule.
> It's carbon surrounded by four hydrogen atoms. It's not all that
> chemically stable. If you mix it with oxygen, you get reactions that
> product carbon dioxide and carbon monoxide, but there is really very
> little oxygen in Titan's atmosphere. It's mostly carbon monoxide and
> its orders of magnitude less abundant than methane.
>
> Leaving everything just without thinking about sources of energy like
> ultraviolet light, methane would last pretty much forever in Titan's
> atmosphere. But the ultraviolet light coming from the sun breaks apart
> the methane. It can break off any one or all four of the hydrogens
> attached to the methane. Usually in the chemistry that goes on, one or
> two of the hydrogen atoms are broken away from the carbon, and the
> result is that fragments or chemical radicals, things that have one or
> two, sometimes three hydrogen atoms attached to the carbon, are left
> behind. These are very chemically reactive.
>
> So methane gets broken up. Instead of CH4, we have CH2 and CH3. What
> happens to the hydrogen? In the giant planets of Jupiter and Saturn,
> the same chemistry occurs, but the hydrogens linger in the vicinity of
> the methane, they don't leave because the gravity is so strong. So you
> simply make methane back again; it's this whole chemical cycle.
>
> But Titan is fundamentally different, and this is a very important
> point about Titan which is key to understanding its evolution. They
> hydrogen atoms, which are very light in weight, escape from Titan's
> atmosphere. In fact, Voyager, at ultraviolet wavelengths, saw a crown
> or corona of hydrogen surrounding Titan. So those hydrogen atoms,
> which are represented as light bulbs on the right side, escape from
> the atmosphere. Now you're left with less hydrogen, and relatively
> speaking, more carbon from this process of breaking apart the methane.
> So you will not get methane back again from the fragments, CH2, CH3,
> CH fragments. There is not enough hydrogen to put methane back
> together again.
>
> So instead, you get a variety of chemical compounds, the simplest of
> which are other so-called hydrocarbons, carbon hydrogen compounds,
> which have a higher ratio of carbon to hydrogen than does methane. The
> carbon to hydrogen ratio in methane would be what? Can someone answer?

W One to four.

Jonathan Okay. So that ratio is going to be higher in ethane in the
settling, which are the simplest products of this chemistry and are
shown on the figure. Ethane is two carbons and six hydrogens, so it's a
ratio of one to three. Acetylene, is C2H2, it's two carbons and two
hydrogens, a ratio of one to one.

Once these are made, unless there is some source of hydrogen we don't
know about, that is the end state of the methane. It has been destroyed,
and other heavier hydrocarbons have been made from it. The ethane, in
the settling, don't stay in the gas very long. They condense out to form
aerosols and will sink to the surface.

Other types of compounds are formed, too. If you click forward to the
next slide, you'll see nitrogen, which I've represented, molecular
nitrogen, two nitrogen atoms stuck together, that's the primary
component of Titan's atmosphere. I've represented that as two blue
spheres. Nitrogen is not very chemically reactive, so it doesn't
participate very often. But when it does, it can make compounds like
hydrogen cyanide, one carbon, one nitrogen, one hydrogen. It can also
make a series of carbon and nitrogen compounds called nitriles,
cyanogens, acetonitriles, go through the organic chemistry book and pick
out anything that doesn't have oxygen, and it's possible you could make
that in the upper atmosphere of Titan. All these things condense out in
aerosols and solid partials and sink down to the surface of Titan.

The essential point here is that ultraviolet light, shining on methane
high in the atmosphere, removes the hydrogen, the hydrogen is lost to
space and the product of this chemistry are things other than
methane---ethane, acetylene, cyanide and various other compounds,
including the folenes(?) you may have heard something about, which Carl
Sagan and colleagues simulated in their laboratory in Cornell some years
ago. Those simulations now are still going on by others at JPL,
University of Arizona, Penn State, various other places. It's not to
hard to make these kinds of compounds in the lab. Just be sure you have
good fume hoods because they're poisonous.

How much of this stuff is made? If you take the rate of which methane is
being destroyed in the atmosphere today, which is simply the rate which
the ultraviolet light is breaking apart methane and you assume you never
run out of methane, then you can make a layer on the surface of this
material, an equivalent layer on the surface, hundreds of meters deep.
The picture is if methane is supplied from some source, then these
aerosols that rain down over time would bury the surface of Titan to
adapt the many hundreds of meters, almost a kilometer.

But there is not enough methane in the atmosphere today to supply that
chemistry for the whole age of the solar system. The methane is limited
by the condensation, the formation of methane clouds in the lower part
of the atmosphere. You put anymore methane in and it simply rains out.

So if this chemistry has been going on over the age of the solar system,
then there must be a source of methane, either in the interior of Titan
or something supplied from above, a comet or something, and then if this
goes on continually, there should be deposits of hydrocarbon on the
surface hundreds of meters deep, averaged over the surface. Some would
be liquid, some solid.

One thing we were looking for in trying to penetrate to the surface of
Titan is any evidence for these liquid and solid hydrocarbons. The
liquid hydrocarbons would be quite dark; the solids could be a variety
of different colors and kinds of materials. Their presence would be an
indicator that this chemistry is not a rare process but something that
has gone on over long periods of time, and it would indicate there are
sources of methane available to resupply the methane depleted from the
atmosphere. Is that clear? Any questions?

Let's go to the next slide. To look at the surface of Titan, this is ISS
high sensitivity, has been one of the daunting challenges associated
with observing Titan. Even though methane was discovered in the
atmosphere over 60 years ago by the Dutch American Astronomer Kuiper,
it's been almost impossible to see the surface. If you look where it's
labeled optical, that is an image of Titan taken by Cassini at
wavelengths that the human eye is sensitive to. You see this orange haze
with a somewhat bluer haze on the horizon. This is material that's made
in this chemistry I described associated with the destruction of the
methane. It's part of a complex of hazes that linger in the atmosphere
of Titan and obscure the surface of Titan to the human eye, and to
Voyager, which could not see beyond the wavelengths of human eyes.

Cassini, however, has two cameras that operate beyond the wavelength of
the human eye. One is the imaging science sub-system, the ISS, which has
a narrow and wide angle camera. It took the optical picture on the left,
but it also too the near infrared picture on the right which is taken at
a wavelength of .93 microns, which is about 20% longer wavelength than
what our eyes can see, and is in a part of the spectrum called the near
infrared.

As one goes to longer and longer wavelengths of light, the haze, which
is composed of small particles, becomes more and more transparent, and
then you can see further and further down to the surface. However, you
never quite remove the effects of the haze, even out at two micron
wavelengths, which is almost two and a half times where the human eye
can see.

Furthermore, there is so much methane in this atmosphere that as you go
out to longer wavelengths, the methane itself, the gaseous methane, is
blocking the light at most wavelengths, preventing it from getting from
the surface out to space where it can be observed.

Beyond a micron wavelength, one has to pick certain narrow colors where
you can see down to the surface. The ISS cameras can see out to about a
micron, but that's about it, the Visible and Infrared Mapping
Spectrometer can see out to five microns. So it can see the longer
wavelengths, but it's not as sensitive as the ISS camera, and the
sharpness, because it is looking at longer wavelengths, is not as good.

Titan is a tricky place. Nature has designed it to be very difficult to
observe. And even at these longer wavelengths, for example this image
where you see these bright south polar clouds and fuzzy features, the
imaging system is still being effected by the haze. And that effect is
primarily to remove the sharpness of the image to blur out the smaller
scale features.

This is easily illustrated if we go to the next slide, which should be a
picture of the Chrysler building in New York City. These are two
pictures taken with a CCD camera. The detector is similar to what's on
Cassini, but these are the kinds of cameras you can buy in an electronic
store, taken from the Empire State Building, looking to the northeast.
There is the Chrysler building in the foreground, and in the background
in the sunny day image, you can see La Guardia Airport, which is a few
miles away. If you take a similar picture on a rainy day, which is on
the right, you can see the things close but it's hard to see the things
further away. And even thing things close are lacking the shadows which
are available on a clear day, and the shadows give you a lot of clues as
to what the orientation of certain features are.

For example, on the Chrysler building, you see that cornice about two
thirds down. You can see the shadows and that clearly shows you how the
angles are oriented. But on the cloudy day, you don't see any shadows so
it's hard to understand how the orientation is, except we're used to
what buildings are like so the eyes kind of fills that in for us. That
patio has a concave shape, and below, the apartment windows are convex.

Most important is the removal of information at the longer distances so
that behind the Chrysler building, it's very hard to discern what's
present. Even if we stretch the image, which we can see by going to the
next slide, now we stretch the image, the shadows are still gone, we see
things a bit more clearly, for example, you can see the angle of the
picture is slightly different in the two, but you also notice that for
the more distant features, you can see essentially white and dark blobs,
but you can't see the sharp details, those are lost.

These very beautifully designed detectors, the CCDs which have been used
on large telescopes on the Earth to look at Titan, used on the ISS
cameras, on Cassini to look at Titan, how ever sensitive they are, they
can't defeat the laws of physics that say when the light is scattered,
you lose the sharpness and information in the images.

So how do we get down to look at the surface of Titan below these layers
of haze? There are two ways to do it. One is to go out to long enough
wave lengths where we are no longer impeded by the haze, and for that
matter, we're no longer impeded by the methane absorption. You have to
go all the way out to radio wavelengths to do that, way out to the
radio. But the sun doesn't emit very much radiation at radio wavelength,
so we need to bring our own source of illumination with us to image
Titan's surface at radio wavelengths from the Orbiter, and so the
Orbiter carries a radar system, which is simple a system the provides a
source of illumination at radio wavelength, bounces them off the surface
and receives them back at the space craft.

The other way to get around the haze problem is to just go below it with
the camera. That is what the Huygens probe did. I want to show you what
the surface looks like with these two techniques, one is radar and the
other is the visible images taken by the Huygens.

Let's go to the next slide titled Radar Probes the Surface Unaffected by
the Haze. I said the radar system on Cassini is designed to bounce radio
waves off of Titan to measure how long those radio pulses took in going
from the space craft to the surface and back, and to measure frequency
shifts so that you get information on how those pulses were scattered
both along the track you're moving and across the track, and the
strength of the pulses that come back tells you which areas are radar
bright and radar dark.

Radar dark tends to be in this kind of experiment, and this has been
done thoroughly for the Earth from aircraft and the shuttle, there is
the JPL radar that has flown several times on the shuttle. It's also
been done for Venus, the entire surface was mapped by radar, Venus is
covered by optically dense clouds as well. The Russians did this first
with ... 15 and 16, then the U.S. did this with JPL Magellan spacecraft
which mapped the entire surface of Venus at radar wavelength. So we have
experience in the solar system with radar imaging for three places:
Venus, Earth and Titan.

In radar images, a dark area tends to be either very smooth so the radar
signal is bounced away from the radar itself. This radar is not bouncing
the waves directly on the surface at normal incidents. It's always
bouncing these at an angle. So anything smooth is going to bounce that
radar signal away from the receiver and you won't see anything. Anything
that's rough but oriented away from the radar will not show a signal,
and anything that has a composition that makes it very radar absorbing
will also appear dark.

Anything that appears bright in a radar image is either very rough so
there are plenty of facets that reflect the signal back to the antennae,
or it has a slope, a topography, that gives you a hill pointed directly
toward the radar, so you get a mirror reflection, or it's a very radar
bright reflective material like water ice. So anyone of these could be
in place. It takes a lot of interpretation to understand what you see in
a radar image. They're not always unambiguous. There are various
possibilities. You have to look at the context.

The wavelength here is a few centimeters, which is much longer than the
wavelength of light. So when I say something is rough, that means it's
rough on the scale of a few centimeters or inches. The best resolution,
the smallest features we can see in the radar are somewhere between a
half kilometer and a kilometer. Now if the ISS were not effected by the
haze, Cassini gets close enough that you could get pictures of Titan's
surface with a resolution of 20 meters. But the scattering in the haze
reduces the resolution in the camera system, and coincidentally reduces
it to about a half a kilometer. So the radar and imaging system give you
about the same resolution, but the radar actually can do that over a
larger area. The imaging system gets a half kilometer only under very
particular conditions where you're looking straight down and right
through the haze.

Our best tool right now with the Orbiter for getting details on the
geology over broad swaths is actually the radar system, and the globe
you're seeing now in this slide shows the two places where radar strips
have been made. The top one was done in October during the first close
fly by of Titan by the Cassini orbiter, and the second one, near to the
equator, was done just last Tuesday evening on Cassini's fourth pass by
Titan, the one right after the Huygen's pro-admission. We call that one
T3. The one on top we'll call TA. We can get into why the ordering of
the fly bys mixes letters and numbers later.

Let's look at what the radar can show us on the next slide. One thing
the radar gives us evidence for is a kind of volcanism, and this is
partly addressing the question of why Titan has an atmosphere. The two
radar images you see are both from the October fly by. The smallest
features you see are about a half kilometer, or a third of a mile
across. The size of the image typically is a couple hundred kilometers
by a couple hundred kilometers. The panel in the upper left looks like a
set of ridges that you might see caused by compression, mountain
building, things being squeezed together, material coming out on to the
surface and being built up in some way.

On the lower right, that second image shows a much softer feature with
rounded edges or low based flows, as they're called. This is what we see
on Venus or even the Earth in places where basaltic volcanism has
occurred, where thick viscous lava flows have come out on to the surface
and flowed in such a way that they create these rounded features. Does
Titan have basaltic volcanism? The answer almost certainly is no. Before
I say why I think the answer is no, let's go to the next slide.

There are similar features in the data from last Tuesday, T3 data, but
they're not quite as distinct and regular, and that's on the next slide
entitled Weaker Evidence for Volcanic Flows. If we go to the slide which
shows a graph and picture of Titan cut away, let me explain why it's
unlikely that Titan has molten rock coming out on to its surface.

If you look at this picture partly stripped away, this is a model of
what Titan's interior probably looks like, although we will not know for
sure whether this is reasonable or not until some later fly bys where
the space craft Cassini Orbiter will measure the gravitational field of
Titan in detail. But, like Ganymede and Callisto, Titan is half rock and
half ice, and during formation, these materials heated up enough that
almost certainly, the rock and ice separated, perhaps completely. The
rock is heavier, denser than the ice, so it would sink to the center,
and the ice would stay near the top. Just as in the case of the Earth,
the metal, the iron, had sunk to the center of the earth, the lower
density rock has surrounded the iron core to make a mantle. On Titan,
it's an ice mantle and a rocky core.

That ice is not just normal, everyday ice which we call ice one. There
can be high pressure ices which are called HP ices here. And if there is
some ammonia present, ammonia is an antifreeze that will lower the
melting point of water ice and allow for a liquid layer to be present in
the interior present as well.

But leaving aside the ammonia for a moment, if the rock is toward the
center, it's difficult to get that out on to the surface because it's
very deep, the density is higher than water ice, it's just implausible
to think about it rising to the surface and coming out. So what causes
these low based flows?

Well, if it's not the rock, it must be the ice. Titan's heat flow, the
amount of heat coming out today, is about 7% the heat flow of the Earth.
It's much less than the Earth, but it's still a number respectable
enough to melt some of the ice in the interior, especially if ammonia is
present to lower the melting point of that ice.

Now, even melting ice and getting liquid water creates a difficult
situation for let's call it ice volcanism or ... volcanism or water
volcanism. Liquid water, we all know, is denser than water ice. How do
we know that? Experiment. Icebergs or ice cubes in a drink, either way.
The Titanic would never have happened if liquid water were not denser
than water ice. That's why we have icebergs. Liquid water is 7% denser
than water ice, and it's really hard to overcome that density difference
and get liquid water out on to the surface. Furthermore, liquid water is
runnier than the kinds of flows we see on Titan in the radar. Liquid
water by itself would not produce those thick, low-base flows we see in
the radar image. I'm trying to show that with that graph which you don't
need to worry too much about in terms of details, but it plots a
mobility index against the gravity of various different objects listed
there, Enceledus, Areil, Tritan, Titan, Ganymede, moon, Mars and the
Earth. Titan would be very close to the G value for ...

Anything on that graph that's high is very run. Anything that plots low
is very stiff or gooey. Liquid water is a very runny substance. Ammonia
water is actually a very gooey substance. And at its minimum melting
point, it has about the same stiffness as the salt does. So on an icy
body where ammonia water mixtures are running out as a kind of cryogenic
or low temperature lava, they would have the same material property as
basaltic lava does on the Earth, and we expect to get very thick flows
from this ammonia water solution.

So if ammonia is present inside Titan, it does three very nice things
for encouraging this cryo-volcanism. Number one, it lowers the melting
point of water by 100 degrees Celsius. Number two, it actually lowers
the density of liquid water to the point where the liquid can rise up
through the ice one layers. Number three, it lowers the mobility of
running water to make flows that look like the salt. Not to oversell
ammonia, I think it's kind of the miracle substance that could give us
very nice cryo-volcanic flows on Titan.

Let's go to the next slide labeled Impacts. There are very few impact
craters on Titan, which is indicative of a youthful surface. The two
definite impact craters that have been seen were seen in this last radar
pass on Tuesday evening. One of these shown on top is over 400
kilometers in expanse, and has a very interesting crater floor to it
that may, in fact, be flooded with liquid hydrocarbons or other things.
The one on the lower left is smaller, it's 60 kilometers across, but
it's much fresher. Here you see something really recognizable. If you
worry about radar giving you recognizable signature of something, this
is really a beautiful impact crater. You can see the rim. The
illumination in these radar images is from the top down so the top,
upper rim on the smaller crater is in shadow, that's why it's dark. The
rim at the bottom is directly facing the radar illumination, so it's
bright. And around the crater is a rough, bright area which is probably
a blanket of ejected material thrown out.

Was there a question?

Okay, materials thrown out during the impact process. So these are
almost certainly impact craters, but these are the only two found so
far. And while these are radar images, the camera system on the Orbiter
should be capable of seeing craters of roughly this size, in fact it saw
the bigger one before the radar did. But the imaging system has, while
it's covered more of the surface of Titan, really has only seen one or
two candidate impact craters, and that is very few impact craters.

If we go to the next slide, here is another moon of Saturn, Tethys,
which is not geologically active, and it's filled with craters. It has
hundreds of craters on the visible surface which is roughly equivalent
with the surface area that has been covered so far by one of the radar
passes. If Titan were geologically dead, if it were not being resurfaced
or not being buried by organics, if other things were not happening, we
would expect to see hundreds of craters on the surface, even leaving
aside the fact shown in the marginal note on the right, that the
smallest impactors would be screened out by the atmosphere. We should
see plenty of craters that are tens or hundreds of kilometers in
diameter, and so far there are only two. So this is a youthful surface
that has been modified so that essentially everything from the first
three quarters of the history of the solar system has been erased on the
surface of Titan.

Let's go to the next slide just to show you some weird things that the
radar has seen.

M I've got a question. The fact that the atmosphere on Titan, you have
fewer craters. But still there seems to be more craters found than you
find on earth.

Jonathan Actually, that's not true. The Earth has a number of impact
craters that are still present on continental platforms. Lake Manicawaga
is the eroded down remnant of an impact crater which happens to be a
lake now. There is Meteor Crater in Arizona. There are several impact
structures in Australia. In fact, on the stable continental platform,
you do see remnants of craters. They tend to be heavily eroded because
of the action of water. But there actually are more impact crater
remnant structures on Earth than we've found so far on Titan.

Briefly, these two other features I don't really have explanations for.
This bright area that looks like a cross section of a flea, these look
like rough channels where material has flowed down to a bright plain. It
might be akin in radar wavelengths to what we saw at the Huygen's
landing site at optical wavelengths. We'll go to the landing site in a
minute. The bottom image shows the linear dark features that at the
moment, there is not a good candidate explanation except possibly their
windblown or fluid driven dunes that were either formed in liquid or
wind. This just illustrates the extreme diversity of geology that we're
seeing in Titan. This is a very diverse, active, complex world. Both
these radar images are from the Tuesday night pass.

Now let's go on. The probe was another way to look at the surface, by
taking a camera below the haze, we can image the surface directly at
wavelengths not too different from where the human eye can see. You all
know when the probe descent occurred, mid-January. I think you can look
forward in the next month or so to some images better processed,
blemishes removed, more detail shown. The imaging team for the Huygen's
probe camera are working at going to the next level of processing beyond
these initial releases.

But if you look at this slide that says Descent Imager and Spectral
Radiometer, the story jumps out at you. The story at the landing site is
that that area has been modified by liquid erosion. I'm showing two
images, one from the side looking imager and one from the downward
looking imager of the same area. These are images taken from about ten
kilometers as the probe descended. You can see the atmosphere is still
hazy. These dentritic patterns, these features are self-evident. If you
look at stereo images, you see they actually drain down into the dark
plain.

The dark plain itself, which is roughly where the probe landed, did not
have a sea of liquid methane exposed, at least where the probe hit, but
there was methane just below the surface. The next slide, an amateur put
together from the DISR panoramas, a nice rendition which illustrates the
darkness of the overall terrain. That area where that 10 kilometer size
scale shown, that's the dissected highland where the fluvial features
were, and that's almost certainly liquid methane because it requires a
very runny fluid to make those kinds of patterns.

The probe landed where the arrow is indicating, in the dark plain in an
area where there are lanes of brighter features, and those are
apparently pebbles debris was seen in the landed image, which we go to
next.

The next slide shows an image after landing. Those pebbles are between
10 and 20 centimeters across. They're solid but not very strong. The one
in the foreground is broken, it was probably broken by the probe. The
surface is generally soft, like wet sand. There is a rigid layer that
may be the pebbles that the probe hit first, we don't know which. Just
under that surface, based on the chemical sniffer, the mass
spectrometer, which detected methane coming out as the landed probe
heated the ground underneath, there is liquid methane present, and it
may have been put there by rain, it may be the storage repository for
the methane that supplies the photo chemistries. We don't know how much
is there, but the out gassing continues, even as the instrument itself
became cold and lost sensitivity. So there was plenty of methane there,
and we saw where it was draining out in that highland area where the
fluvial features were. It's draining down into the stark plain.

In terms of evidence, this is still circumstantial, but it's good
evidence that there is a lot of methane at and within the surface that
is supplying the stratospheric methane for the chemistry, and is
creating a lot of the erosive features we see on the surface of Titan.

There is, however, some chemical evidence that most of the methane we
see was out gas recently, it has not been there for a long time. This is
a story that deserves to talk unto itself. Basically, each chemical
element that forms the dominant constituent of Titan's atmosphere, the
nitrogen that's in N2 and the carbon in methane comes in different
isotopes. Isotopes are the same element, but with different numbers of
neutrons. By measuring the ratio of the isotopes of nitrogen and carbon,
and comparing them to Earth, we can tell how long this material has been
in the atmosphere. The nitrogen has an enriched, heavy isotope component
relative to the earth, to suggest that the nitrogen escaped early on,
and that's preferentially enriched the atmosphere in the heavier
isotope, and the lighter isotope is the one that preferentially escaped.

The carbon, the methane does not have the same isotopic enrichment. It's
identical to the Earth, and that suggests that the methane has not
participated in the same escape process as nitrogen did, and so at least
some of it was out-gassed later in the history of Titan. So this graph
is one possible scenario whereby methane initially comes into the
atmosphere, is depleted by photo chemistry with time, and then late in
the history of Titan as the interior cools down and the ice itself cools
and is less able to hold methane, more methane comes out, and that's the
methane we see today. This is one possible suggestion that Titan is
continuing to out-gas methane.

I have a few concluding slides. The first is the evidence for ammonia as
a key player in Titan's evolution. I talked about ammonia as a substance
that mixes with water, that makes cryo-volcanism easier and gives you
the shapes of flows we see in the radar data. That's the first point on
the graph. The second point is that ammonia will allow a liquid layer to
remain present and stable in Titan's interior over the age of the solar
system. This is consistent with a characteristic of Titan's orbit,
mainly that this orbit is not circular but eccentric, it's shaped like
an oval.

If Titan has a liquid layer early in its history that then froze over,
as we would expect for pure liquid water, the freezing of that layer
would cause tidal dissipation, enhanced friction in the interior that
would generate heat at the expense of the eccentric orbit, the orbit
would circularize. The fact that this orbit is not circular (is
eccentric today), and not circular suggests that that liquid layer has
always been present.

Finally, this last bullet, which I didn't update from AAAS presentation,
that's why there's this odd reference to Toby Owen here. It refers to
the fact that the chemical sniffers on the Cassini Orbiter and Huygen's
probe both detected no stable, primitive noble gasses, Argon, Crypton,
Xenon All very under-abundant. That is an indirect signature that the
nitrogen we see on Titan came from ammonia. But why is that?

Well, the nitrogen that's in the atmosphere today, molecular nitrogen is
a fairly volatile species. It's difficult to trap and waterize. It likes
to be in the gas phase. If it came in as molecular nitrogen, in
primordial, primitive ice debris. You'd expect to have lots of the noble
gas argon because it's just as volatile as nitrogen, chemically it's
very similar, so if large amounts of nitrogen were trapped in the
material that went to form Titan, there should be a lot of argon trapped
as well, and we should see an argon abundance that is large. We see no
argon, which suggests that the planets out of which Titan formed were
warm enough to exclude argon, they were warm enough to exclude nitrogen.
The only way to get a nitrogen atmosphere is to bring it in as ammonia
which contains nitrogen, and then convert that ammonia to molecular
nitrogen, which we see today. That's an indirect chemical argument, but
it's one that has been theoretically suggested 20 years ago as a test
for the origin of Titan's atmosphere, and the lack of argon seems to
have its simplest explanation in this chemical argument that supports
the idea that lots of ammonia was brought into Titan as the source of
the nitrogen atmosphere.

Next slide, the absence of craters, the substantial geology we see on
the surface, the erosion, the evidence for burial, some very dark areas
in the radar that could be liquid hydrocarbon, these are all suggestive
of a very active history for Titan, one that involves ammonia water
coming to the surface, methane being out gassed or converted to higher
hydrocarbons and nitriles, and then condense out of the atmosphere and
bury the surface in places. These are all consistent with a lack of
craters.

I'll leave you with one last slide to whet your appetite. Those
interested in chemistry might want to think about the following. This is
now the \<gap\> amino acids, sugars, etc. The hydrocarbons and nitriles
that are made in Titan's atmosphere, in the absence of oxygen and liquid
water are not very interesting to the origin of life. Ethane is ethane,
hydrogen cyanide is hydrogen cyanide. But mix them with liquid water or
ammonia and you potentially get all sorts of interesting things, amino
acids, nucleic acid bases, sugars, things shown on the diagram. If Titan
has had periods of cryo-volcanism, ammonia water flows, then these would
have mixed with the organic deposits on the surface, and some chemistry
during that period of time before those flows froze over could have
produced some of these very interesting prebotic species. We can't
determine wither this makes any sense or not from Cassini-Huygens, but
given the evidence for deposits or organics and liquid methane on the
surface here and there, I think it's a strong case that we want to go
back to Titan to sample the most interesting areas of the surface with
mobile platforms. One thing we'd like to do is look for some of these
prebotic molecules which, if they are present on Titan, would be an
interesting prospect, indeed.

I thank you for your time. I'm happy to take questions.

M I teach astronomy with an emphasis on astro-biology. I was very
enthused and motivated about everything you spoke about, but especially
the last thing you spoke of. If we do indeed find evidence of these
nitriles and hydrocarbons combining with liquid ammonia and producing
things like amino acids and sugars, what would you say, is it possible
with the lack of oxygen in the atmosphere that there could possible be
any type of aerobic life at all?

Jonathan Most life on Earth as anaerobic. Biologists like Lynn Margolis
would say that most of the action has been in the anaerobic bacteria
over most of the Earth's history. We're the last hurrah once the
atmosphere became oxygen rich. So you're not going to have aerobic life,
and probably not even life such as we know it on the Earth because the
length of time that liquid water can exist on the surface is relatively
short, and ammonia water flow might give you liquid water with ammonia
for decades, perhaps. A large impact into the crust would melt the water
ice and it might take thousands of years for the bottom of the crater to
refreeze. Those are times that are long for an organic chemist, but
short for a geologist.

The place is so cold that you're not going to have stable liquid water.
But during the time you have that liquid water and ammonia exposed to
the hydrocarbons, there is interesting chemistry that goes on, and we
could learn a lot from the frozen remnants of that chemistry because
it's a natural laboratory where that chemistry would have gone on on
large spatial scales over the scale of a flow or a crater, for time
scales that are a lot longer than the career lifetime of an organic
chemist. So there is some interesting prebiotic information potentially
on the surface of Titan.

Finally, if you talk to imaginative organic chemists like Steven Benner
at the University of Florida who has thought about how life might exist
without liquid water, he would argue that there is the potential for
thinking about organized chemical systems even in liquid hydrocarbon.
Liquid methane, we know, is stable at the surface of Titan today. So
that would be a very exotic form of a chemical system that, would we
want to call it life or something else, it's not clear. But you could
imagine that maybe there are some interesting autocatalytic cycles going
on, hosted by liquid hydrocarbon in ways very different from life as we
know it.

His point, and I'm paraphrasing Steve who was featured in the New York
Times Science Section about this in January, he's say we should not
dismiss the idea of complex chemical systems, even if we don't have
liquid water. My point would be there are brief times and places where
we do have liquid water, and let's try to find the preserves remains of
the products that are made when that water was liquid.

M Another question about the low land areas. If we've got erosion, some
places have to be lower, are you looking at maybe techtonic forces
creating depression, lowlands for these fluids to flow into?

Jonathan It's possible. One of the interesting questions is, at the
Huygen's landing site, what is the lowland area? One way to do it is to
have what a geologist would call extensional tectonics where you're
pulling two pieces of this ice crust apart, so you have a depression.
Another way to do it is have an impact crater that forms and gradually
gets filled in, and you have a basin, as well.

One of the problems with the Huygen's landing site is it has not been
covered by the radar yet. Our first chance to do that will be on the
eight Titan fly by, and we only get a little piece of the landing site.
It's not very well covered by the radar. The really good coverage is
late in the mission. It would be nice to bring that forward, but it's
difficult to do because the timing of the flybys is dictated by the
overall tour of the spacecraft in the Saturn system. But once we get
radar data over the landing site, we'll be able to get the geological
context. We'll see if those dark plains are lowlands, and whether they
look like the result of tectonics or and old, eroded crater form that we
can't really recognize well anymore.

It's an excellent question. It could be tectonics, could be the remnants
of impact basin. Hopefully from the Huygen's landing site, we'll learn
the answer to that before the primary mission is over.

M About your last slide, wasn't the probe able to detect sugars and
amino acids?

Jonathan No. The probe carries a gas chromatograph and mass
spectrometer. The mass spectrometer goes up to a mass of 140. So in
principle, it could detect some smaller fragments, the simplest amino
acids, sugars, etc. But those are going to be very non-volatile. The
sampling that occurred in the atmosphere of the non-volatile components,
the aerosols, was done by sucking the aerosols into a pyrolizer, which
heated them and broke them into smaller fragments. So now you've lost
the information you would have on sugars and so on.

On the surface, the probe, because it was warm and had a 20 watt lamp
and the chemistry instrument had a heated inlet, it was vaporizing stuff
for basically an hour to an hour and a half while the probe returned
data from the surface. There might be conceivably, at the upper mass
end, some of these interesting things. But they'd have to be there in
abundance to be seen by this GCMS, because the sensitivity is not high.

These chemical instruments take a long time to analyze when they're on
spacecraft because you can't go back and recalibrate the same instrument
you use to make the measurement. So it will take months to get a full
mass spectrum out of that GCMS and see what some of the fragments are.
We're at the beginning of that.

If there are some interesting oddities at the high mass end, we might
want to begin to think about the possibility that it's seeing
interesting fragments like this. If there is more oxygen in the deposits
than expected, that's exciting, too. Right now, all we know from the
mass spec is lots of methane at the surface, maybe some benzene that's
showing up, too. But we'll have to wait for the full analysis. Again,
because of the design and limitations inherent in Huygen's probe, we'll
probably have to go back with a state of the art mass sect GC designed
to look for these things.

M Did the pyrolizer have a GC?

Jonathan The pyrolizer was actually hooked up to the GC so the products
were pyrolized and sucked into the GC.

M That's not clear in the diagrams.

Jonathan The pyrolizer works, and there are some GC data that do show
peaks, etc, but they have not yet been analyzed. The guy who is the PI
for this experiment is an extreme stickler for detail. His point of view
is better to get it right than get it early.

So for the Galileo probe which went into Jupiter's atmosphere was just a
mass spectrometer. The probe got much hotter on the inside than the
designers at Hughes had calculated. So Niman had to go back with an
engineering unit and do the calibrations all over again. It was the
better part of a year before he came out with a mass spectrum, but it
was right, well calibrated. Patience is what's required.

M But the maximum mass on the pyrolizer, I thought that was like 400.

Jonathan Ultimately, the GC can handle higher molecular weight stuff,
but the products of the GC that come then analyze by the mass spec, and
you're still limited to the 140 AMU. So from the pattern coming out of
the GC, we may get some indirect evidence for higher molecular weight
stuff, but we won't get a mass spec identification of those for any of
the higher molecular weight stuff.

M ... but what about a higher propio nitrile or something? They would
still fall below 140.

Jonathan Yes, those you could see. If you've got stuff that's best
explained with things that have oxygen attached, that's exciting, too.
So there are some potential ways to get at this chemistry. We don't
expect to see those in the atmosphere, we expect only to get that from
the surface analysis because that's where the mixing with the water
would occur. In a way, that's nice. You have the atmospheric analyses as
the kind of background, the non-oxygen components, and if you see
something different at the surface that has oxygen, that would be
exciting, but it's still TBD.

M Have you actually detected ammonia?

Jonathan No. If we don't see it before the end of the mission I'll have
to take all this back and destroy my viewgraphs. The part of the problem
is that the compositional spectrometer on the Orbiter, the VIMS
instrument, can see ammonia but it's working around these methane
absorption features in the near infrared. So those have to be removed,
and they block out large parts of spectrum. So if you make a
spectrum---and if you e-mail me I'll send you a reference of a paper of
this in press and we show ammonia and water and which bands are blocked
out by the methane. It's daunting. But there are people trying to work
in the clear windows to see if they can see evidence for ammonia.

On other airless icy bodies, ammonia doesn't last very long because it
tends to get photolized by UV. On the surface of Titan, it should last a
long time. So if there is exposed ammonia on the surface that's not
contaminated with this organic dust falling down, we ought to be able to
see it. I'm hoping we will.

Ken I'm Ken Kramer. How do we e-mail you?

Jonathan You're all welcome to e-mail me at <jlunine@lpl.arizona.edu>.
If it didn't come through clearly, I give Trina permission to forward
the e-mail address.

Ken How much water is there? We keep talking about water, but how much?
Do we have an estimate?

Jonathan Water ice is something else that people are trying to identify
in the VIMS spectra. From the bulk point of view, based on the density
of Titan, it should be about half the mass of Titan. Titan is about 10
to the 26 grams total mass. So we're talking a lot of water. Ganymede
and Callisto have the same density, they're airless bodies, and when you
take spectra in the near infrared, you see lots of water on the surface.
So by analogy, we expect the same is true for Titan. But it's covered by
this atmosphere. The surface is dark and it obviously has this organic
deposit on it. So we've got to get that VIMS spectrometer looking at
places that are bright and have been cleaned off by methane rain or
something else. There are a couple of candidate areas where it looks
like there is this water signature, but it's just difficult. It's a
question of being able to see through these deposits and the atmosphere.

The DISR, the camera on the probe, also had a spectrometry mode, and
they do see signature of water ice in part of the landing site area. So
there are exposed deposits of water ice in the landing site.

Ken How do you get, as chemists, nitrogen from ammonia?

Jonathan There are two ways to do it. For all the non-chemists in the
audience, ammonia is NH3, it's a nitrogen with three hydrogens. If you
have an ammonia atmosphere and you expose it to ultraviolet light, you
will get molecular nitrogen, the ammonia will be converted to hydrazine
and then nitrogen. Again, on Titan, because the gravity is so low, when
you break the hydrogen off of the ammonia, the hydrogen escapes so you
can't make the ammonia back again. You're on a one way trip to molecular
nitrogen.

The other way to do it, which may have been more efficient, is if you
have an impacter coming into the atmosphere, the chemistry that occurs
and the shock behind the \<?\> will also convert the ammonia to N2.
There were actually experiments done at NASA AMES years ago that show
that that's the direction the chemistry goes. Since we expect that Titan
and the rest of the Saturn system had a high impact rate early in its
history, it would make sense that that would be a time when the ammonia
would also be converted to N2. So this low gravity on Titan, which
removes the hydrogen, is really the key to this directionality of the
chemistry going from ammonia to N2.

Mark This is Mark Weiss in New York. How much of the chemistry we've
learned about Titan recently relates to early Earth history?

Jonathan Some of it does. The Earth has a nitrogen atmosphere. We don't
think it started out as ammonia, but there might have been some ammonia
present. More relevant, though, especially recently, there has been a
trend toward invoking methane in the atmosphere of the Earth as a way to
enhance the early Greenhouse effect on the Earth Our astrophysical
colleagues tell us the sun much have been much less luminous early in
its history, ... evolution says the sun was 30% less bright. Yet at the
same time, this is four billion years ago, the first 10% of history of
the earth.

But you look at the rock record and there are sedimentary and
metamorphic rocks, so there was liquid water present at the time. So how
do you keep the atmosphere warm enough if the sun is 30% less bright.
You have to have a bigger Greenhouse effect. Initially, people said it's
more carbon dioxide. But it turns out that that's not enough, and you
should see some evidence of that in \<?\> and so on.

More recently, people like Jim Cassy and others have said maybe there
was substantial methane, and that methane is going to be broken apart by
ultraviolet sunlight. So the early Earth atmosphere may have had a kind
of chemistry going on akin to what we see today on Titan, with the
methane being broken apart. But then there was also much more CO2 in the
Earth's atmosphere than we have on Titan.

Finally, some of the organic chemistry that might be going on if the
organics are mixed with liquid water, presumably, are mimicking the
early steps towards life on the Earth, although that's more speculative.

Mark I guess we have to go there to find out.

Jonathan It's always tiring to hear people say we need more data. But I
believe Titan could have turned out to be a bust, a kind of a Calysto, a
dead cratered world surrounded by a hazy atmosphere. But it wasn't. It's
very dynamic and diverse, and I think it's an excellent target for a
follow up mission. What you need is mobility and the ability to access
the surface. But Titan gives you some advantages, a thick atmosphere,
low gravity and low temperatures makes it great for aerial vehicles. In
fact, JPL has been studying using blimps to move sensors around on the
surface. It's just very easy to do that. The thing that's not easy is
the enormous distance. It takes a long time to get there because it's a
billion miles away. But once you're there, it's actually not a bad place
to explore with aerial vehicles. So yes, I think we have to go back.

Chuck Chuck Marlboro from Central Valley, I'm a NASA Solar System
Ambassador. For the last eight years, I've run a amateur radio net with
about 250 members on space science. We always solicit their questions.
Some of these may seem a little silly, but they're questions they want
to know.

Number one, I'm sure must be dying to see the radar imagery of the
Huygen's landing site, but you mentioned that would happen later. What
would be involved in moving that up higher in the schedule? Isn't it
just pointing a camera, or do you have to change all the space craft
trajectory as well?

Jonathan It's the latter. The radar, because it's sending an active
pulse of radio waves to illuminate the surface, only works when you're
within 5,000 kilometers of Titan, you have to be close. So you can only
do it around closest approach, about 40 minutes around closest approach,
plus or minus 20 minutes. The area that you're covering is determined by
where the close approach point is on Titan. That point is actually
determined by the fact that the Cassini Orbiter uses Titan's gravity to
change the spacecraft's orbit, or I should say that JPL uses Titan's
gravity to change the orbit around Saturn of the Cassini Orbiter itself.

Everyone of these fly bys is designed so that the timing of close
approach will give you the right orbit around Saturn after the close
approach. What does the right orbit mean? It means an orbit that gets
you by some of the other moons, good views of the rings, gets you behind
Saturn for experiments that are called Occultations most importantly,
gets you back to Titan so you can change the orbit again. So if you want
to change the close approach point, the timing, you have to burn rocket
fuel to change when you do that close approach, and then you have to
burn rocket fuel afterwards to get back on the course you were
originally on to make sure you get back to Titan and do all these other
high value targets.

That's the long answer. The short answer is what does it take? It takes
burning rocket fuel, and that's fuel we could use for an extended
mission.

Chuck To paraphrase, it's possible, but highly impractical. Is that
correct?

Jonathan No. It's possible, but it's just costs you. It depends on how
much you want to use it. There is an examination being done of whether
these close approach distances could be tweaked so that you get somewhat
better coverage of the landing site in T8, for example. What it costs
you is rocket fuel. In some cases, you have to move the close approach
point so much that it is impractical. In other cases, it's possible but
you would be using fuel that would shorten any extended mission that
might be envisioned for 2008 and beyond.

Chuck At the present time line, when do you feel you'll have radar
images of the landing site?

Jonathan My understanding is T8, we get a piece of it, not the closest
approach but sort of on the wings of the radar imaging.

Trina That's October of 2005.

Jonathan Right. We get a really good shot of it on T41. Trina, do you
know when that is?

Trina That's February, 2008. And there is a chance of getting it on T37,
which is November of 2007.

Chuck My goodness. A long ways to wait.

Jonathan Right. Then you always get into these almost philosophical
issues of do you grab these high science targets now and use up a lot of
fuel because if you don't, maybe the spacecraft won't be there tomorrow.
It's working fine now, but who knows. Or do you play it conservative and
use as little of your consumables as you can. It's a Hobson's choice.

Chuck We're going to get the data anyway and we've been waiting six
years to get there. So it's best we opt to go with the normal plan. A
couple of other layman questions. One of our net members saw the
European's space agency press conference where one scientist mentioned
that Titan's atmosphere is flammable. Is that a true statement?

Jonathan That press conference cost me a night in Chicago because I
helped put it together and then I caught in the Chicago snowstorm. It's
only flammable if you bring oxygen. The nitrogen is pretty inert. The
methane, if you expose it to oxygen, of course that is quite flammable.
What prevents it from exploding is that there is not very much oxygen in
the atmosphere. All of the oxygen is bound up in carbon monoxide and
carbon dioxide and there is actually very little of it.

Chuck So there's not enough oxygen there to create ignition. A lot of
folks got concerned and said what would happen if you lit a Bic lighter
theoretically on Titan? Nothing would happen, would it.

Jonathan It wouldn't light.

Chuck Very good. One last question.

Jonathan Before you ask it, another interesting thing is if we want to
drive around on the Earth, we have all the oxygen and we put our
hydrocarbons in a tank, that's the gasoline. On Titan, if you want to
drive around, there is lots of hydrocarbons and you just want to bring a
tank of oxygen.

Trina That's great.

Jonathan So it's just the opposite.

Chuck Some of the images they saw coming down from the Huygen's probe
looked a little bit like there were some fuzzy areas around some of
these white areas. They speculated, could we be seeing some fog or out
gassing from the ground in those images?

Jonathan I'm very interested in that, too. There could be some fog. I
think we'll learn more when these images are better processed. You could
actually have fog. You could have methane or ethane fog near the
surface. The meteorological conditions are right. I don't think you need
out gassing. I think if it turns out those areas are foggy, it's a
metrological effect, a weather effect.

Chuck Outstanding. Thanks for being with us and for coordinating this
whole CHARM teleconference.

Trina Jonathan, thank you very much. We really appreciate you taking the
time today. if people could stay online for a few minutes, I wanted to
have an open question. We've sort of gone through the term telecom
taking the most recent interesting thing that's happened on board the
spacecraft. I'd like to get some ideas from you guys as to some topics
you'd like us to cover. We've hit all the major topics so far---rings,
Titan, icy satellites, ... the only one we haven't had is Saturn's
atmosphere which I'm trying to set up. Other than that, do people have
any ideas of some things in particular they would like us to try to get
a CHARM telecom on?

Chuck My net members keep asking me what is the plan for ending the
mission at end of life? Are we going to plunge it into Saturn like we
did Galileo into Jupiter or send it on its merry way? Is there a plan
yet?

Trina There is no plan. Of course, our plan is to have a very long and
productive extended mission, although they are talking about sending it
into Saturn at the end. But no hard plans on that as of yet. Any other
topics?

M I think it would be very helpful to have telecoms at the appropriate
amount of time, say a week or three, after the upcoming close fly bys of
the various icy moons. For instance, another shot an Enceladus next
month, perhaps the third or four weeks in March, it would be interesting
to look back at those images and talk about that.

Mark This is Mark Snyder. I think it would be interesting to have
something on planetary formation. All the extra solar planets they
found, I think it relates a lot to---he's talking about title
dissipation models as far as eccentricity of the orbits and stuff, and
how to circularize the orbits. I think with all the stuff in there it
would be interesting.

Trina That's perfectly fine. One of things we wanted to do with these
CHARM telecoms, Cassini-Huygens analysis and results of the mission is
we wanted to give the scientists an opportunity to be able to discuss in
depth and in context, things that you wouldn't necessarily be able to do
in a press conference. I think planetary information, in fact Saturn
system formation is a very good topic.

Anita We have a lot of educators that call into us. I was wondering if
you could do at least one session on education offerings. Particularly,
maybe there are some folks out there who have things they've done,
things they've learned they would like to share.

Trina Okay.

Ken Good idea. Success stories, for example, writing rings work, so we
could apply it other places. That would be good.

Trina Okay. We might want to do that one separate from CHARM where we
really just focus with the educators. There might be more of an interest
to that sub-group than the whole group so we might want to have a
special one on that.

Anita I know, at least, the museum folks, they like to share what they
themselves...

Terry This is Terry Hillburn in San Diego. I'd like to see a specific
teleconference on each one of the instruments and the data it brings
back.

Trina Instrument overview.

Terry Yes, one per instrument and some data from whatever pass they have
available to talk about.

Trina That's a great idea. In fact, we'd split that up. We'd put all the
ORS instruments in one, and all the MAPS instruments in another and a
microwave instruments in a third. We might be able to do all the
instruments in two hours, but that may be too much.

Terry Do them in separate groups if you could. I've taken that
information in the PowerPoint and give a monthly update in the astronomy
club meeting on that stuff, and they love it.

Trina You're right. It's really good to have instrument overviews to
internalize what each instrument---because the spacecraft is very
functional.

Terry And if you could attach a human point of view to it, like that
poor guy whose machine didn't get turned on, that even draws the
audience in better. I'd like to talk to the guys who actually work with
it and hear what they have to say.

Ron This is Ron Smith in Belleview, Washington. Another thing is we get
these Cassini status reports every week, and there are terms and
terminology in there that is sometimes not obvious, the reviews for
different tours, the VIMS cubes and the something to do with high water
marks that show up in the status reports. If that could be put into more
layman's plain English.

Trina Now that I think about it, even if we have an instrument overview,
we might like to also have a spacecraft overview. Everybody probably
knows the basics of it, but if you spend a couple hours learning about
the spacecraft, that would be interesting. The details, like the
attitude control system and why we do something called the high water
mark and what it accomplishes.

M And the fact that they use Titan so many times to change the orbit,
get a new orbit or whatever.

Trina Yes, the tour overview. Why we drive the tour, or how we drive it.

Ron Something to do with fly wheel and how you use that and manage the
energy.

M I think it would nice to hear something from the DSN people, too.

Trina Okay. Now of course, the group that hosts this, the Project
Science Office that hosts the CHARM telecom. Of course, the last five
topics we have are all outside the Project Science Offices per view, but
that doesn't mean we can't arrange it.

Jonathan We can try.

Trina Yes. Any other topics? Terrific. Our next CHARM telecom will be
the last Tuesday of March, March 29^th^. I currently do not have a
topic. We have a big Project Science Group meeting next week in
Florence, Italy, so I'll try to round up several scientists there to
support the CHARM telecom in March. I think everyone for attending. You
guys have a great month.