Titan shoreline?

On Tue, 18 Jan 2005 22:49:04 -0500, Michael McCulloch
wrote:

I think Titan has just moved ahead of Europa in the missions planning
department at NASA/ESA. It is much easier to land on Titan than
Europa. You also don't need to drill through 2 to 19 km of ice,
depending on who you ask, to investigate.

Good point. It's a big positive to have a nice thick atmosphere to act
as a natural 'brake'. All you need after you get through the
atmosphere is a nice large parachute to get you to the ground. Even
Mars with it's thin atmosphere can't offer that kind of weight
savings. However you need a lot more propulsive force to get to Titan,
but the positive there is that since you're landing on Titan you don't
need all that fuel that Cassini had to carry to brake into Saturn
orbit.

On Tue, 18 Jan 2005 23:48:29 +0000 (UTC), (Brian Tung)
wrote:

Scott M. Kozel wrote:
The gas giant planets are believed to have a layer of liquid somewhere
below the atmosphere, but those planets are not believed to have a
"surface" like the terrestrial bodies have; it is probably a gradual
transition from gas to liquid with no real definite "surface" point.

Hmm...what would a semi-gas, semi-liquid "look" like, so to speak? Fog?

Sounds like what happens beyond the critical point of a gas-liquid
phase transition. For example, from the wikipedia:

http://en.wikipedia.org/wiki/State_of_matter

"... the phase boundary between liquid and gas does not continue
indefinitely. Instead, it terminates at a point on the phase diagram
called the critical point. This reflects the fact that, at extremely
high temperatures and pressures, the liquid and gaseous phases become
indistinguishable."

Nick

--
Nick Theodorakis

contact form:
http://theodorakis.net/contact.html

Wasn't it Nick Theodorakis who wrote:
On Tue, 18 Jan 2005 23:48:29 +0000 (UTC), (Brian Tung)
wrote:

Scott M. Kozel wrote:
The gas giant planets are believed to have a layer of liquid somewhere
below the atmosphere, but those planets are not believed to have a
"surface" like the terrestrial bodies have; it is probably a gradual
transition from gas to liquid with no real definite "surface" point.

Hmm...what would a semi-gas, semi-liquid "look" like, so to speak? Fog?

Sounds like what happens beyond the critical point of a gas-liquid
phase transition. For example, from the wikipedia:

http://en.wikipedia.org/wiki/State_of_matter

"... the phase boundary between liquid and gas does not continue
indefinitely. Instead, it terminates at a point on the phase diagram
called the critical point. This reflects the fact that, at extremely
high temperatures and pressures, the liquid and gaseous phases become
indistinguishable."

I remember seeing a demonstration of this effect at the London Science
Museum many years ago. They had a pressurised vessel that contained, I
think, liquid CO2 held at a pressure and temperature close to its
critical point. Initially, the chamber is clearly half full of
transparent liquid. When you push the button to start the device in
operation, it changes the conditions in the vessel to a point beyond the
critical point.

All you see is that the meniscus between the gas and liquid phase
gradually fades away. The refractive indexes of the two phases, which
were initially quite different, change to become the same. The meniscus
holds its shape as it fades until just before it disappears, when it
breaks up and looks a bit like the swirly effect you get when you mix
alcohol and water.

When the process completes, the vessel contains CO2 in what we consider
to be its normal state. An invisible "gas".

When the process is reversed, small faint droplets appear. Hard to see
at first because the refractive index is almost the same as the
surrounding material. The droplets soon become more clearly defined and
merge together like a separating emulsion until all the liquid is
gathered together at the bottom of the vessel.

--
Mike Williams
Gentleman of Leisure

"Paul Neave" wrote in message
...

But why does everyone seem to fervently want liquid lakes and oceans of
any
type to be proven? Not just Titan but moons like Europa as well? It is
what
it is.

We're just looking for another world akin to Earth - as far as we know,
we're the only planet with oceans of any liquid on its surface. A solar
system full of dry, cratered dustballs is a bit dull!

It would be a bit dull, but people have got to be a bit more dispassionate
about it. I'd love to see crashing waves of liquid methane breaking against
the shoreline on Titan, but it's still an interesting place to visit and
explore even if it doesn't work out like that. And so would Europa.

- MJP

To me all of these supposed 'craters' look like droplets of liquid in the
atmosphere which it is supposed to have. Either that or they are artifacts
on the cameras. But they dont look like craters to me. If there were craters
you would see very large ones as well at these tiny looking ones. No to me
it definitely looks like a sea of liquid with tributaries flowing into it of
some sort.

Whatever they are Titan suddenly must have become the most interesting
object in the Solar System and we must go back to map the surface properly
and look for signs of life! America should stop wasting money on the useless
space station and start getting manned missions to these places. A
permanently manned moon station must also surely be a priority for this
decade to act as a refuelling point.

--
Regards
Nats

"It's life, Jim, but not as we know it."

"Angelo Campanella" wrote in message
...
jochta wrote:
Thierry wrote:
"Angelo Campanella" wrote in message
...
You are 100% right.
For example, those small "holes" in the surface close to the draining
channels and in the plain are too suspect (same size, shape, etc) to be
true craters. But my opinion is only say 75% sure.
But on other images, there are craters like on this one
http://web.mit.edu/bitbucket/Titan/airstrip.jpg

Though many items appear to be depressions or craters (dark hue), they are
accompanied by an element of white hue as well. This smacks suspiciously
of differentiation, aka edge detection, or 'sharpening' performed
intentionally of accidentally. Too many such spots have the same
attributes.. this makes me believe that they are not craters. I see some
white spots over the lake as well. Craters usually have better definition;
a fully circular ring, a flat core bed, usually depressed, but mostly
flat, as are clearly evident on the surface of our moon.
But, as on earth, moderate craters have long since weathered away. Some
vestiges are evident on earth, but they are rare. If via these recent
photos we are to believe that we see a lake and streams on Titan, then we
have to accept widespread erosion. The lake, puddle and stream liquid,
could be a mixture of ethane and ammonia since there is abundant nitrogen
on Titan. The liquid would be a mixture, like our gasoline.

Any water ? surely not. Knowing that water can not sublimate at those
temperatures, it can only found on the ground as ice or snow. melted
with a large proportion of other components.

Water will be ice, perhaps of a different phase or crystal structure than
earth ice via low temperature and crystal grouth sans liquid water.

We must also know that at those
temperature ice of ammoniac, co2 or methane are unstable.

I don't see how they could be unstable unless there is a mechanism at play
(photosynthesis) that would produce some oxygen from water. The only
instability I see via these photos is "weather related", as in our
rainstorms, winds, waves and washes.

It is more than probable that if we found some liquid it will be methane
in
phase close to its freezing point.

methane boiling point (1 atm) = 109K, melting point = 91 K.
ammonia boiling point = 240 K, melting point = 194k
carbon monoxide boiling point = 82 K, melting point = 78 K

And if there had ice of methane in
these lake, they 'd sink.

More likely melt.
Ammonia ice is more likely.

I could not find ethane and propane BP or MP in my Chem-Phys handbook.


Angelo Campanella

Titan
orbit mission. Aerobraking has been used sucessfuly at Mars with the
MGS and Odyssey orbiters.


Lets just hope they dont mess up metric and english units again and perform a
titan "lithobraking" manuever :0

take care

Blll

BllFs6 wrote:

Titan
orbit mission. Aerobraking has been used sucessfuly at Mars with the
MGS and Odyssey orbiters.

Lets just hope they dont mess up metric and english units again and perform a
titan "lithobraking" manuever :0

European teams use SI units and so don't suffer from the same conversion
problems that NASA encounters with its contractors working in those
quaint antediluvian units that Americans blame on the English.

Odd really since the US signed up to metrication a very long time ago...

Regards,
Martin Brown

Martin Brown wrote:
European teams use SI units and so don't suffer from the same conversion
problems that NASA encounters with its contractors working in those
quaint antediluvian units that Americans blame on the English.

Those antediluvian units, in context, might have been SAE, which doesn't
refer to England in any way. (SAE stands for something like Society of
Automotive Engineers.)

Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt

John Harper AE5X wrote:

I don't know MJP, the argument for liquid seems fairly clear to me:
http://www.ae5x.com/titan.jpg

Wow, they're out of scale too!