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

**FTS-NASA-VOICE**

**Moderator: Trina Ray**

**March 25, 2008**

**1:00 pm CT**

Coordinator: Good afternoon and thank you for standing by for today's
conference call. Today's conference is being recorded. If you have any
objections, you may disconnect your lines at this time. Now I'll turn
the meeting over to Ms. Trina Ray. Ma'am, you may begin.

Trina Ray: Thank you very much and welcome everyone to the Charm Telecon
for March of 2008. We have a very exciting topic today. Dr. Chris McKay
is a planetary scientist up at NASA Ames and is an expert in
astrobiology. And there's a lot of interesting astrobiology out in the
Saturn system both with Enceladus and Titan, and so we're very pleased
to have him with us today, and looking forward to a really terrific
talk.

Everyone is welcome to ask questions if they'd like during the
presentation or questions at the end is just fine. And with that, I'll
turn it over to Dr. McKay.

Chris McKay: Great, thanks and hello to everybody. Happy to be talking
to you about Titan and Enceladus which are clearly the two stars of the
Saturn system with respect to astrobiology and in fact, in the whole
solar system.

I want to start -- let's look at slide 1. And the title is Organics on
Titan, Water on Enceladus. And that summarizes why these worlds are so
interesting to us from an astrobiology point of view.

On Titan, we find all sorts of organic products being produced by the
photo chemistry in the atmosphere. And on Enceladus, there's as you all
know, jets of water ice coming out from the South Pole. Well, these are
the reasons why these objects are so interesting from us from an
astrobiology point of view.

I want to start by a little motivation with the slide 2. Why is life on
other worlds interesting? And it's useful to think about what we're --
why we're searching for life in other worlds when we talk about what
we're going to look for.

To my mind, the real interest in searching for life in other worlds as
it says here in slide 2, is the possibility of finding a second genesis
of life. It's not just finding life, but finding alien life, something
that's different, has a different origin then life on earth. And
presumably therefore we have a different chemistry.

Why is that interesting? Two reason. One is as I say here, comparative
biochemistry. If we had a different type of life with a different
chemistry we would be able, for the first time, to do comparative
biochemistry, which we can't do now because we only have one example of
biochemistry, namely that chemistry on earth.

So if we found alien life, we'd be able to see what other ways is it
possible to do the biochemistry that leads to life? And that could have
deep implications for our understanding of biochemistry which of course
could have implications for everything from our understanding of
diseases and pest control agriculture and everything that's rooted in
our understanding of biochemistry.

So it could be enormously important scientifically and practically. The
other implication of finding a second genesis of life is that it would
provide convincing evidence that life is common in the universe. If we
could show that right here in our own solar system, life started twice
independently, then that would be convincing evidence that life is
common in the universe.

And as you see on slide 2, I've added my own little editorial comment
there, "Yay, it would be great to know that, that life is indeed common
in the universe." With one example, we can't really make that
conclusion, but with two examples, we can, the big difference between
one example of life and having two separate examples. So that's what
we're looking for.

Well, let's go to slide 3 and of course, you've seen these before.
There're jets of water on Enceladus. And as you know, Cassini just
recently did its deepest fly by yet through these jets with interesting
results, in fact, that they're going to discuss at a press conference
tomorrow.

So the jets coming out of Enceladus were a big surprise hit from an
astrobiology point of view and there's still debate as to what is the
origin of these jets, where they're coming from and what their cause is,
but from an astrobiology point of view, the model that has the most
potential is the model in which the jets are coming from a sub surface
water system.

If we go to slide 4, the representation of what this sub surface water
system might be -- some sort of pocket of liquid water below the
surface, venting through cracks in the ice. If that's the case, that sub
surface pocket of liquid water is a really interesting target in terms
of the possibilities of life. So that's where I want to focus on.

If there is such a sub surface pocket of water, and I emphasize that
that's only one of the models for explaining the geysers. If there is
such a sub surface pocket, is it a likely target to life?

So if we go to slide 5, the question we're asking has two parts really.
Given liquid water on Enceladus -- and we're going to assume that for
the rest of this talk -- is there a plausible origin of life on
Enceladus and a plausible ecology for that life?

And I separate these problems because it's important to separate them
because there may be places in the solar system where life could survive
but it hasn't originated. And there may be places where at one time life
originated but it no longer persists because there's no longer an
ecology habitability and energy to support it. So we're going to ask
both of these questions.

Unfortunately, when we talk about the origin of life, we don't really
know what we're talking about. We don't have a theory for the origin of
life. And so slide 6 shows the best we can do which is to diagram all
the different origins for the (series) of life that has been proposed
for earth and try to apply it for Enceladus.

Now when we look at earth, we know that there's life on earth. We can
look out the window and see it. We don't know how it got here. We don't
-- we do not -- have not yet solved the mystery of the origin of life on
earth, but there's no shortage of suggestions for how life got here.

So this diagram on slide 6 shows these various suggestions organized
according to categories. And the fundamental category is life started on
earth versus life didn't start on earth. Life came to earth in the
material that formed the earth. That's called panspermia.

But most people favor the theories in which life did start on earth and
there's various modifications of that. All of these theories are
suggested for earth but some of them could also imply -- apply --
equally to a sub surface (aqua ferrone) Enceladus and I've marked those.

Obviously if panspermia is true, material that formed the solar system
had dormant organisms in it and these dormant organisms fell into
environment and then grew if the environment was suitable then these
same spores should've been contained in -- could've been contained -- in
Enceladus, so that's okay for the origin of life.

But also, the theory, the so-called warm primordial soup theory which in
this diagram is called endogenous production of organics, in which the
environment started off with a mix of organics and water and life
emerged from that mix. Well that might've happened on Enceladus if the
materially that formed Enceladus was rich in organics and if it formed
out of commentary type material, it should've been.

Another theory for the origin of life is that life originated in
chemical systems like in the -- such as would be occurring at the bottom
of the ocean with sulfide rich water coming out of the bottom of the
ocean reacting with iron or other materials in the ambient environment.

That is, in fact, right now probably the most popular theory for the
origin of life on earth, the current popular theory. That might also
work in a sub surface environment on Enceladus.

So the conclusion would be, with respect to the origin of life on
Enceladus, is we don't know if life could've started on Enceladus, but
then we don't know how life started on earth. So our ignorance is not
necessarily indicative here, but given our -- the range of theories for
the origin of life on earth, some of those, many of those, could also
apply for Enceladus, so we have reason to be optimistic that life
could've gotten started on Enceladus.

Let's turn now to the second question, if there was life on Enceladus,
could it still be going today? Could this liquid water environment still
be habitable? Could there be a plausible ecology? So if we turn to slide
7, I've listed some approaches to understanding whether an environment
has a plausible ecology.

Well one is to base it just on laws of physics and people love to do
this and they speculate about life forms that live off (ecnotic) energy
sources like electric fields and thermal gradients. It's not very
satisfying.

The second approach is to focus on (extremafiles), certain organisms
that can do seemingly extreme survival tricks, radiation resistance,
salt tolerance, et cetera.

But the third approach that I list here is the one that I favor and I
think is more plausible, which is to look at actual ecosystems, to go on
earth to places where there're actually microbial ecosystems that are
living under the environment that we postulate on another world, because
organisms don't obtain energy from all the possible physical sources and
individual (extremafiles) do not a community make, and so actual
ecosystems are really the most -- the best way to approach the question
of plausible ecologies on Enceladus

And to live on a sub surface aquifer on Enceladus would mean that we're
talking about microbial ecosystems that could live without light,
they're deep below the surface, and without oxygen. There's no reason to
think that Enceladus would have built up oxygen like we find on the
earth. And as we know, of course, for most of earth's history, earth
also didn't have oxygen.

So we want to find ecosystems on earth that live without oxygen, without
light. And in fact, there are -- we now know, and these are recent
discoveries in the last ten years or so -- three ecosystems that are
really profoundly isolated. And isolated -- as we look at slide 8 -- I
give these examples, and I define what I mean by isolated.

Isolated means that they survive without oxygen, they survive without
light, and they survive without organic input. That's pretty amazing. No
light, no oxygen, no food. They really are completely self-reliant. We
have three ecosystems known. Two, as shown here, are based on methane
production where they basically are eating hydrogen that is released
from rock reactions with water. So water reacts with basaltic rock, it
releases hydrogen, hydrogen plus carbon dioxide provides an energy
source for this community.

And there's an example of this discovered in the deep basalts in the
Columbia River Basin more in the border or Oregon and Washington, and
there's another one discovered in the faults in the Idaho Falls. So we
have two of these ecosystems both based on methanogen.

A new one was discovered recently in the mines in South Africa where the
energy is based on chemistry produced by radioactive decay. So radiation
decay produces hydrogen and peroxide and that generates a reaction
scheme shown in the next slide, slide -- we're now on slide 9, showing
in slide 9, the reaction scheme for this energy source provided by
radiolysis, radioactive decay.

Radiation splits the water to form hydrogen and to form oxidants. The
oxidants react to form sulfate and then sulfate reducing bacteria use
that as an energy source, so these three ecosystems, two methanogens and
this one sulfate reducing bacteria system, live completely independent
of the rest of the bio systems. They don't rely on sunlight. They don't
rely on oxygen made by plants or oxygen in any form. They don't rely on
food, organic material produced by other organisms.

These are examples of ecosystems that could survive in the aquifer of
Enceladus. And they're interesting because they are an entire community
of organisms. They are -- the primary producers are defined. In the
first case -- two cases, it's methanogens and the second case -- third
case rather, it's sulfur reducing bacteria. But there're other organisms
in there completing the food web so these are complete ecosystems that
cycle materials and nutrients through them.

So an example of how -- for -- the next slide, slide 10, shows an
example of how this might work on Enceladus. So here is, for example,
the methanogen based ecosystem. If the methanogen based microbes are
living in the water, they're consuming hydrogen and CO2 producing
methane. If that methane rich water is recycled down deeper into the sub
surface of Enceladus, and it sees higher temperatures, temperatures
above 500 degrees Centigrade or so, that methane will cycle back to
hydrogen, which could then be released in the water, completing the
cycle and the organisms could potentially be consuming this geologically
produced hydrogen and CO2.

That's a system that we can now point to and say we have examples on
earth of microbial ecosystems that could work with exactly this
mechanism and we would predict that one of the products of such an
ecosystem would be methane. And interestingly, methane is seen in the
plume in Enceladus.

Now often when we talk about Enceladus, people mention the deep seas
vents on earth. Go to slide 11, I've shown pictures of these vents and
the worm tubes that are associated with them. But these are not good
examples for Enceladus. They were not on my list of plausible
ecosystems. And the reason is, is that the metabolism at these vents is
based on the consumption of oxygen.

The chemistry that powers these vents and that powers the wondrous
ecosystems associated with the vents, the clams and the (worms), is the
oxidation of hydrogen and sulfide. Well, oxygen that they -- these vents
-- are consuming is produced at the surface of the earth by plants. So
it is not true that these vents are isolated from the surface. It's
sometimes stated but it's incorrect. They require oxygen.

Now it may be that below the surface of this vent, away from the oxygen,
there are anaerobic chemo auto tropic ecosystems that don't require
oxygen. But this has yet to be determined.

So the next slide, slide 12, shows a picture of the Stardust space
craft, kind of a rough sketch. If the plume of Enceladus is really the
vents from a biological reaction chamber, then the stuff that's flying
out in that geyser should contain bits and pieces of these organisms
that are living in this sub surface chamber.

So one possible mission design would be to fly through and collect those
pieces and bring them back. And Stardust is a mission that has collected
bits of a comet's tail and brought it back. It flew through the plume of
a comet and brought the material back to earth.

Well that same spacecraft or a derivative of it could fly through the
plume of Enceladus and bring some of that material back to earth and we
could then do a lot more detailed measurements then we could do on
Cassini. Cassini is flying through the plume and is giving us a lot of
good data but it wouldn't be able to say search for organisms, whereas,
if we brought a sample back through Stardust -- through a Stardust like
spacecraft, we could.

So let's imagine we do that. Let's imagine that in a future mission, we
fly through Enceladus and collect material and bring it back to earth.
How would we be able to tell that that material is a second genesis of
life?

So in slide 13, lucky 13, I phrased that question. If we find organic
material in the plume of Enceladus, or on Europa or Mars for that
matter, how can we tell that it was ever alive? Now presumably, the
material that's come through the plume of Enceladus into space is dead.
It's been -- although it may have been alive in the sub surface aquifer,
by the time it comes flying out in space and collected by a Stardust
like spacecraft, it will have been dead from exposure to the vacuum and
solar ultraviolet and so on.

So what we're probably going to have in our collector are dead
microorganisms. Well, how do we recognize dead microorganisms? Well if
they're like us, if they have the same biochemistry and genetic material
as life on earth, well then recognizing them is easy. We can use the
techniques we've developed to study life on earth and recognize
earthlike life anywhere.

We could, for example, amplify their DNA. We have the capability through
PCR and other techniques to see DNA at extremely low levels. We could,
in principle, recognize one bug it that microbe had DNA in it.

But so if it's like us, then it's easy. But remember what I said at the
beginning, what we're searching for is alien life, so we're hoping it's
not like us. We're hoping it doesn't have DNA, that it has some other
mechanism for encoding genetic material. That would be a more
interesting case.

We'd like it to be alien but as I say here in slide 13, if it's alien,
then that's hard because we don't know how to search for alien life. We
don't -- we can't amplify its DNA if it doesn't have DNA and we -- if we
don't know what it's using for a genetic material, we don't know how to
amplify that. So that's the hard case, but it's also the interesting
case.

So how could we approach that? What would we do with this material that
we collected from the plume of Enceladus? Well I want to make a
suggestion of course, and slide 14 is the suggestion of how we would be
able to recognize some sort of alien life that's so different from us
that it doesn't have the same biochemistry that we have. It doesn't have
the DNA and RNA and maybe it doesn't even have protein.

So what would we look for then? Well, slide 14 shows what I call the
Lego Principle. And the argument here is a rather simple minded
argument, and that is that biology, as we observe it, is largely built
up from a small number of components stacked on top of each other.

That's how Legos work. Legos work, you get a bunch of blocks that are
all the same, but by stacking the blocks in different ways, you can make
all sorts of different things. So the complexity of constructions in
Legos comes from the combinatorial possibilities of what you can do with
just a small number of different blocks.

Well that's how life works. The Lego blocks of life on earth are the 20
alamino acids which go in to form the protein, the five nucleotide
bases, which go in to form RNA and DNA, and the D sugars which go to
form the poly saccharides. And with these blocks, the giant scaffolding
molecules of life are built -- the proteins, the nucleic acids, and the
poly saccharides.

And they're built like Legos -- stacked. The proteins are good examples.
With those 20 amino acids stacked in different ways, a whole arrange of
proteins are possible which do everything necessary for life. And I have
argued that this modularity principle, this Lego principle, is likely to
be a common property of biology as well as mass produced children toys,
throughout the universe because it's more efficient.

It's more efficient for organisms to tailor their enzymes and bio
chemical machinery to just a few molecules and to use those molecules
repeatedly. It's the same reason that a house made out of bricks, all
the bricks are the same size. It's a lot easier to handle, manipulate,
design a structure if the basic module is all the same, so that's what
we call -- or what I've been calling -- the Lego Principle. Life is like
Legos. Built with blocks.

Well the next slide, slide 15, shows what the Lego blocks of earth life
are. This is a -- the Lego kit for life on earth, the building blocks of
earth life. In that diagram here you see the 20 amino acids, the purines
and (perimadines) that form the nucleotide basis, the sugars, a few
alcohols and fatty acids. And that is the Lego kit of life. Earth life
is built from these basic bio-molecules.

Well that's good. Alien life, however, could be built from a different
set and that's an important point. Life on earth uses this set, alien
life could use a different set and it would still satisfy what I'm
calling the Lego Principle.

And an example of that is building things out of Legos but also building
things out of, say, Lincoln logs. When I was a kid, they didn't have
Legos. Legos hadn't been invented yet. In fact, plastic hadn't even been
invented yet. We played with wooden blocks called Lincoln logs.

Well anything that you can build with Legos, I could've built with
Lincoln logs. You know, you could imagine a table. Let's imagine two
tables. One table built out of Legos and one table built out of Lincoln
logs. Both of them will function as tables. Well ecologically they're
similar. At the microscopic level they're also similar. Both Lego blocks
and Lincoln logs are built out of carbon atoms.

Legos, the carbons occur in plastic and Lincoln logs, the carbon occurs
in wood. So it's interesting. A table made out of Lego logs and a table
made out of Linc -- out of Lincoln logs are the same at the highest
level. They're both tables. And they're the same at the lowest level.
They're both made out of carbon atoms. But they're different in the
middle. They're different in the way the carbon atoms are arranged to
form the building blocks from which the structures are made. We call
that biochemistry.

So alien life could have the same elements and it could have the same
ecology and it could have different biochemistry. That's the clue that
we might look for when we search for alien life, but it's got to have
some sort of biochemistry.

An example of why life has to choose certain molecules is shown in the
next slide, slide 16. This shows the amino acids which are one of the
Lego blocks of life on earth. When life only uses the L amino acid, the
left handed amino acid in protein, life doesn't use the D amino acids in
protein. Life has to choose.

These -- in protein, these amino acids are stacked on top of each other
but they only stack if they all have the same handedness. It's like
driving on the road. It doesn't really matter whether everybody drives
on the left or the right. We all have to agree to drive on one side.

Well it's the same with molecules. It doesn't really matter whether life
uses left, L or Ds, but it's got to use one or the other. Earth life
chose L. This is the basis of what's the Lego Principle. Life has to
choose. Life can't just use all the organic molecules. It's not
efficient. It chooses some and uses them to the exclusion of other
similar molecules. Here, life uses L. It doesn't use D.

Slide 17 shows how we might turn this into a search strategy when we get
a sample of dead stuff from Europ -- from Enceladus. Slide 17 shows the
distribution, a theoretical distribution of molecules where I've plotted
the number of molecules versus the type, in some general characteristic
of type.

A non-biological distribution should be smooth, statistically smooth.
All the different types should be there at some relative concentration
depending on their chemistry. Biology would not show that kind of
pattern. Biology would show discreet concentration of molecules at very
high levels only.

So in the middle of this diagram I'm showing this -- it looks like a
picket fence. Those might represent the L amino acids and the spaces
between them might represent the D amino acids. In a non-biological
distribution, both the L and the D would be present at roughly the same
amount.

But in a biological distribution, the L amino acids are much, much more
concentrated then the D amino acids, so biological distribution looks
peculiar compared to the smoothness of a non-biological distribution.
And that we think is a general characteristic of life, is that it's
going to choose molecules and use them and not others.

So slide 18, the next slide, shows what we hope to find say on
Enceladus. We might find that there there's a certain set of molecules
that are used. It's not a smooth distribution. And what's more
interesting is that the molecules are different then the molecules we
use.

That would be evidence of life, even though all the organisms we'd be
studying might be dead, we don't need a live organism to find evidence
of life, interesting paradox due to the way life in English means many
different things. It means an individual organism. It means the
metabolic processes of that individual organism and it means the
collective phenomenon of many individual organisms and it means the
essence of that phenomenon even separate from the organisms themselves.

So in a sense, when we search for life, we're searching for a word
that's very hard to define in the English language, much less to define
biologically. But dead alien microbes would be evidence of life and they
could be evidence of life if we could show that they have a discreet
pattern or molecules that they use but similar to evidence of life on
earth. And it would be interesting if we could show that they were a
different set of molecules. That would prove that it was a second
genesis.

So the exciting thing for me about Enceladus is the chance that we will
find in the plume of Enceladus, dead microorganisms and be able to
examine those microorganisms to see if they represent a different kind
of biochemistry from the biochemistry we have on earth. So that's
Enceladus.

Let's now turn to Titan where we have an equally exciting but very
different possibility for astrobiology. So Titan, slide 19, we see the
image of Titan taken from Voyager in fact, many years ago, showing
Titan's organic haze. Titan is surrounded by an orange cloud of organic
goo. Well that's interesting because it makes us think about Titan and
earth and the earlier -- organics on the early earth. And in fact, in
many ways, Titan is very much like the earth.

Slide 20, next slide, shows the comparison of Titan and the earth.
Titan's gravity is less. It's about the same as the moon but its
atmosphere is very similar. Titan is the only world in the solar system
of all the moons and planets, only Titan has an atmosphere that's within
a factor of 10 of the pressure of earth.

It's also the only object of the solar system that, like earth, has an
atmosphere dominated by nitrogen. It's also a world which has
hydrological cycles. It has rivers and lakes and rain. But on earth,
rivers and lakes and rain are water. On Titan, the rivers, lake and rain
are methane. Titan also has an interesting greenhouse effect, different
from earth's but it's interesting.

The biggest difference between earth and Titan, is Titan is very cold.
You can see in this comparison, Titan is minus 180 degrees Centigrade.
It's a pretty chilly being compared to earth, plus 15. And that
generates a -- probably from a biological point of view the most
important difference between earth and Titan, earth has liquid water,
Titan does not. Water on Titan is essentially a rock.

And I also show the rotation and solar (unintelligible). Titan has a
liquid. Let's go to the next slide which is the water cycle on earth.
What makes earth such an interesting world? What makes earth a world
that can sustain such a diversity of life is the water cycle. Earth has
water, not just does it have water, but the water moves. Water is in
cycles.

This is a diagram from the U.S. Geological Survey showing the water
cycle and that is the essence of understanding life on earth is
understanding the water cycle. Life on earth is made up of water, lives
in water and is widespread on the earth because water is widespread on
the earth.

Now if we go to Titan, slide 22, what we have on Titan is a methane
cycle. It has many of the same attributes as the water cycle on earth
but it involves liquid methane. It has clouds and rain and rivers but
it's -- they're made of methane instead of water. Keep that in mind as
we think about the possibility for life on Titan.

Let's go back to the organic stew on Titan. Slide 23 shows the known
composition of Titan's atmosphere. These are things that have been
measured in the atmosphere directly. You can see there's a whole host of
organic molecules produced by photo chemical reactions triggered in the
methane and nitrogen. It's a pre biotic reactor.

Next slide shows a laboratory simulation of a pre biotic reactor. If we
take a gas -- a jar -- and we flow through the jar nitrogen and methane
at the same ratio as the current Titan's atmosphere and put a spark
through it, we find that after a few days, the jar turns brown and all
sorts of gooey material is made.

So this kind of non-biological chemistry, organic chemistry, is
occurring on Titan and it's occurring in these jars. And that'
interesting from an astrobiology point of view in what it might tell us
about how life started on earth. Maybe we go back to the theories to the
origin of life and the organic soup theory, maybe this was the organic
soup that was made on early earth and we're seeing the same sort of soup
production going on on Titan. But it certainly has a lot of interesting
organics.

And the next slide shows a sign that we ought to put up on Titan, "This
world contains compounds known to the state of California to cause
cancer." We're required by law to put that up anywhere where we -- in
California where there's anything bizarre chemistry or molec -- or
carcinogens. So Titan would certainly deserve such a sign. It's got a
very interesting chemistry.

But now let's see chem -- is there a possibility that that chemistry on
Titan goes beyond just a model for the origin of earth and goes to life
itself. The next slide, slide 26, asks the question, it says, Titan
Mystery Number 6. Now this comes from a list of Titan mysteries I put
together. It mostly has to do with the physics of Titans, but number 6
was the astro biology (unintelligible).

Are there aliens? Could there be life on Titan? And the little diagram
here, the little cartoon here, is not meant to be an accurate
representation of alien life on Titan. It's just a pretty picture. But
suppose, could there be aliens on Titan?

Well slide 27 puts this in context. Let's compare earth and Titan and
life on earth and Titan. On earth, life is carbon based living in liquid
water. Because it's carbon based and living in liquid water, life on
earth is widespread because water is widespread and carbon is
widespread. There are lots of places on earth where organisms can live
because what they live in is all over the place -- water.

Well on Titan, there's lot of carbon, as we've been talking about, and
there's a liquid that's widespread, but that liquid is not water. That
liquid is methane. So if there was life that could live in liquid
methane instead of liquid water, carbon based life moving in liquid
water, then it could be widespread on Titan, so earthlike life that
lives in water is not going to be doing very well on Titan. There're not
very many places, if any, where there's liquid water on Titan, maybe
deep below the surface but we're certainly not going to get to that any
time soon.

The fact that there's a liquid on Titan's surface really is what's
become the attraction for astro biologists. Could that liquid be a
liquid that support life? We're so used to thinking that water is the
liquid for life. We don't really -- we haven't really given much thought
to the possibility that other liquids might support life.

Maybe liquid water could support -- liquid methane could support life.
Now it would be a very thin, very cold base for life but life could
adapt to that. Then the question is, could that life in liquid methane
have an energy source?

Slide 28 show a calculation which illustrates that there could be life
on Titan energetically, and this is the calculation of the energies of
reaction that would be available organisms on Titan if they consumed
organics and consumed the organics with hydrogen. We know that there's
hydrogen in Titan's atmosphere and we know that there's organics on the
surface and in the atmosphere.

An organism that ate the organics and breathed hydrogen would be able to
generate energy. On earth, we humans and other heterotrophs eat organics
and breathe oxygen and we react the oxygen with the organics. Well on
Titan, organisms could eat organics and breathe hydrogen and react the
hydrogen with the organic as shown in these reactions, essentially to
produce methane.

And the amount of energy released by these reactions are larger then the
minimum energy the methanogens need on earth. So there could be hydrogen
consuming life on Titan and if it's there, it could consume the
hydrogen. Life could be vigorous enough that it could deplete the
hydrogen.

And so the next slide, slide 29, is a calculation of the hydrogen
concentration expected as the function of the biological consumption. On
the left of the slide, is basically no biological consumption. And as
the biological consumption gets bigger and bigger and bigger, it reaches
a point where the biological consumption of hydrogen is strong enough
that it depletes the hydrogen.

That is similar to the way that life on earth, plants on earth in
particular, can deplete CO2 in the atmosphere, a plot of CO2 over the
year, shows it going up in the winter and down in the spring as plants
consume the hydro -- the CO2 in their growth.

Well the same thing would be true on Titan, and the next slide, slide 30
shows what you'd expect, what you'd predict that the (Hoigen's) probe
would've detected if there had been vigorous consuming life on Titan. If
there was no life, the probe should see the red line, hydrogen straight
all the way down to the surface, but if there is life at the surface
consuming the hydrogen, then as the probe got near the surface, there
should've been a drop in the hydrogen concentration.

Well, did the probe see that? The answer is, we don't know. The probe,
in principle, the probe could detect hydrogen but the carrier gas that
the probe used was hydrogen also. So it will take some more calibration
to pull out the hydrogen signal. And the team that is doing the probe,
GCMS, the mass spectrometer, hasn't yet done that calculation.

But if we see a drop in hydrogen near the surface of Titan, the only
explanation for it would be biology, which would be very interesting
because if we found biology on Titan living in liquid methane, we would
know that it was a separate genesis because life on earth is based in
liquid water and if we found life based in liquid methane, we would know
that it represents a completely different independent type of life.

And that would be very interesting because it would suggest not only is
life more widespread but it's also more versatile and it can use other
liquids besides water which is something that, again, we will never know
from just studying the earth because on earth the only life that we know
is based in liquid water.

The next slide, slide 31 is the end, last slide, the end of the talk. So
now what I was thinking is we could have time for questions if there are
any.

Trina Ray: Are there any questions? Well Chris, I have a question. I
know that there's a lot of work being done currently, thinking about the
next big, you know, Flagship mission that NASA is going to start
funding. There's a lot of preplanning work and the big items that seem
to have floated to the top in terms of the targets is Titan and the
Europa mission.

And both of those really do have this, you know, this astro biological
question that is so interesting. If you had your preference, which one
would you like to see?

Chris McKay: Well that's a hard choice. I'm -- I think Europa, Titan and
Enceladus are all good candidates for astro biology missions. I guess if
I was running the show, I wouldn't pick one. What I would do instead was
do smaller missions to all three. I wouldn't do a flagship mission where
I put all my bucks into one mission, send it to one object, I would do
smaller missions to all three, like I would do a Stardust fly by through
Enceladus and pick up some of that stuff and bring it home.

And do an impact sampling on Europa and maybe some thing else on Titan,
but try with smaller missions to go for all three targets because we
don't know which of those three is really going to be the most
interesting. And if we invest in a Flagship mission, we're basically
tying up our assets for the next decade.

And if we pick right, that's great. But if we pick wrong, I wonder.
Like, I wonder about dropping Enceladus off the list. There's a planet
that's spitting out water and that's hard to pass up. So I guess I
didn't really answer your question but I redefined your question.

Trina Ray: Well it was a good answer. They're all interesting targets. I
love your idea of the Stardust collectors through the Enceladus plume.
That's -- I don't know where -- I hadn't heard that yet and I see that
as a fantastically interesting thing to do.

Chris McKay: Yes, and that might be done for much less then a Flagship
mission costs. So who knows? Hopefully managers that are much wiser then
us are working these problems.

Trina Ray: So does anyone else have a question?

(Bob Capital): Yes I do. This is (Bob Capital) in Dundee, Illinois.

Trina Ray: Go ahead.

(Bob Capital): Can we tell the difference between -- it -- looking back
at the slide you said where if we find life like us it's easy but less
interesting.

Chris McKay: Yes.

(Bob Capital): What would you distinguish finding life that's like us
versus, oops, we accidentally had some contamination on the probe and we
found our own life.

Chris McKay: Yes, that's a hard question because if it's like us, it
could be us, quite literally. It could've been from contamination so we
have to be very careful in sterilization and cleanliness. So that's a --
the possibility of finding something we brought with us is always a
concern.

(Bob Capital): Thank you.

(John Scheff): I have a question -- (John Scheff) from Cambridge, Mass.
In terms of these Stardust type collection of possible organic material,
would the space probe move through the plume maybe too rapidly to
collect the particles and keep them intact enough for biological
analysis back on earth?

Chris McKay: Well that would be a design requirement. We want to slow it
down enough so that it could -- that the stuff that's collected didn't
get vaporized and destroyed for sure. I don't know how slow that would
have to be. It'd probably have to be less then relative velocity of a
couple of kilometers per second. But the aero gel collector that was
used on Stardust is very good at catching material without destroying
it.

(John Scheff): Thank you.

Man: Question?

(Earl Kyle) I have a question.

Trina Ray: Go ahead.

(Earl Kyle): This is (Earl Kyle). I'm in Rochester, Minnesota. One of
the Apollo missions brought back a television camera from the moon on a
surveyor probe and when they analyzed it they found the organisms had
survived. Can you comment on that story and how was it that they were
able to survive those many years up there in that harsh environment?

Chris McKay: Yes, that -- there is a report, a published paper
documenting that surveyor camera brought back by Apollo 12, I think it
was\...

(Earl Kyle): Yes, because they landed 200 feet away from the probe.

Chris McKay: Yes, exactly. Had bacteria on it -- inside it.

(Earl Kyle): Right.

Chris McKay: And then -- and this is not surprising really -- LDEF, the
Long Duration Exposure Facility, took back, hurried up into earth orbit
for, it was supposed to be a few months, ended up being six years. And
bacteria survived in that as well. And the explanation seems to be that,
for example, on the moon what would kill organisms would be direct
exposure to the sun, ultraviolet light from the sun.

But organisms shielded, for example, inside a camera not being exposed
to the ultraviolet light from the sun, would only experience two effects
-- vacuum and cosmic radiation, and neither of those would kill an
organism very quickly.

An organism shielded from the sunlight could survive many years in
space, maybe even thousands of years in space before it was killed by
gradual accumulation of radiation.

(Earl Kyle): Okay and my second question was, what are your thoughts
about the possibility of finding life beneath the surface of Mars? I
think the Europeans are designing and XO biological rover that's
supposed to probe six feet down. What are your thoughts about that
possibility of success?

Chris McKay: Yes I think we may also, in addition to Enceladus and
Europa find evidence of past microbial life on Mars. That's a whole talk
all by itself but the answer is yes, I think there's a good chance that
Mars will also -- we will also face the same challenge of how do we tell
that this gooey stuff was once alive, which is why on my slide I said,
for Mars or Enceladus -- or Europa, sorry.

Both those worlds -- three worlds, Mars, Europa and Enceladus, we have a
possibility of finding organic material that may have been alive at one
point.

Man: Question

(Greg Cermak): This is (Greg Cermak).

(Earl Hanlin): This is (Earl Hanlin).

Trina Ray: Okay (Earl), how about you first and then (Greg)?

(Earl Hanlin): Okay, I'm fascinated by your suggestion on a Stardust
mission around Enceladus. I'm wondering, what information could that
type of a mission collect that the Cassini doesn't collect now by flying
through the plumes?

Chris McKay: Well Cassini was not designed as an organic analyzing --
analyzer mission. The most relevant instrument on Cassini is the mass
spectrometer, the ion neutral -- neutral -- ion neutral mass
spectrometer, but it only detects up to atomic mass of 200, basically
detect fragments and small molecules.

What we'd like is to be able to bring the sample back to earth and
detect it with much more sophisticated GCMS than is on Cassini, look for
a more complex organics and Cassini could (unintelligible).

(Earl Hanlin): Okay, thank you.

Trina Ray: And (Greg), your question.

(Greg Cermak): Yes, could you elaborate on any of the current techniques
that would be used to survey any of these ecosystems that you're talking
about possibly, in comparison to those they use on Viking and also
compared to isotropic fractionations et cetera?

Chris McKay: Well I think what we would do, the instrument of choice
right now would be a GCMS very similar to the one that flew on Viking
maybe with higher or a more sophisticated sample preparation mechanism.
But the actual analytical instrument would be a GCMS and it would also
-- it would, as you point out, have the capability to do isotopes but
that's a key -- I didn't mention it in detail, but that's a key feature
of molecules, again, that life tends to select, there're certain
isotopes versus others. So it could be another part of this pattern that
we're talking about in terms of a Lego pattern.

(Mike Hopka): Question.

Trina Ray: Go ahead.

(Mike Hopka): This is (Mike Hopka) is Colorado. What time is that press
conference tomorrow and is it on NASA TV?

Chris McKay: Oh, I don't know the details. I just heard it\...

Trina Ray: The press conference tomorrow is at 11:00 Pacific time and it
is on NASA TV. I believe the panel consists of Dr. (Hunter Wace) who's
the ion and neutral mass spectrometer PI that Dr. McKay just discussed,
John Spencer, who's on the Sears instrument, that's the composite
infrared spectrometer I think. I should know this. And finally, out of
the final panelists, is Dr. (Larry Esposito) who is the PI for the UVIS
instrument, the ultraviolet spectrometer.

Chris McKay: That's good, thanks.

(Jane): And you can go -- this is (Jane) in Cassini outreach -- you can
go to the Cassini Web site and get some information about that press
conference and it's also on the blog, our Enceladus blog, there's a nice
feature about the press conference tomorrow.

(Mike Hopka): Okay thank you.

(Jane): So yes, it'll be streaming on nasa.gov. It'll be, you know, you
can get it lots of different places.

Trina Ray: Okay, do we have any other questions?

(John Smith): Yes question -- (John Smith), JPL, getting back to the
contamination issue, how can we tell if we find life on these bodies
that is very similar to earth, that it wasn't transported, say, from
earth due to an asteroid impact? I've read about transfer between the
planets theoretically.

Chris McKay: Yes that's another possibility in the category of
panspermia if you will, which is that life started on earth and then
impact spread it around the rest of the solar system, or that life
started on Mars and impact spread it around the rest of the solar
system. And then what we'll find is not a second genesis on these worlds
but, you know, our distant cousins who moved in earlier.

(John Smith): Would we be able to tell that it did not start on earth or
will it just be nebulous?

Chris McKay: It'll be hard to reach a definitive conclusion. I think
we'll need other information to -- we have to work it further to try to
understand where it started.

(John Smith): Thank you.

Trina Ray: Okay, do we have any more questions? Okay, hearing none, I'd
like to thank Dr. McKay for joining us today. It was really
fantastically interesting Chris and we appreciate you taking your time
putting together the presentation and spending an hour or so with us
online today.

Chris McKay: My pleasure.

Trina Ray: And the next Telecon will be the last Tuesday in April which
is March 29th but I don't know what the topic is, so we'll have to wait
for (Amanda) to send that out. I'm sure it will be interesting. She has
been doing a fantastic job getting some great scientists to support the
Charm Telecon. And with that we'll sign off and everyone have a nice
month.

Woman: Thanks Chris.

END