Titan flyby

[Stargazer]

Originally posted by: Tormod
There are indeed very intriguing features on the surface, but the resolution is still way to low to be able to make out anything. The shades of gray do not tell us anything, and any color image is false color since the surface is not visible due to the haze (so they need to use infrared, and there are only 5 narrow bands in the spectrum in which the surface appears).

And add to that the problem that these infrared images can't show us any of the topography of the surface, for that they need to use radar, which they have recently done for some parts of the surface.

However, there can also be liquid ethane. Some have suggested oceans of MEthane, but methane only occurs naturally as a gas. Ethane is a favored candidate for oceans or lakes on Titan. Ethane, however, has a freezing point of -135 degrees Celsius, whereas the surface of Titan has an even temperature of -180 degrees Celsius.

I looked up the melting points of both ethane and methane, and they seem to be -182.76 C and -182.5 C respectively, according to Wikipedia. Since -180 C is the mean temperature of Titan's surface, isn't it then possible that there could be liquid methane and ethane?

[Tormod]

My bad. -135 C is the flash point. (That's what I get from sitting up too late...)

I am unable to provide the scientific background, I am just providing bits and pieces in the notes from the presentation.

The scientist in question was Christophe Sotin, from the laboratory of planetology and geodynamics (my translation from French), by the way, and his speech was titled "Titan's mystery: Oceans in the solar system".

He thinks there is an ocean on Titan, and that it may have a depth of somewhere between 100-300 kilometers. But the dense atmosphere and the temperature would form a solid surface widh a width of 50-150 kilometers. As of now I am unable to explain why he thinks so.

Methane does not appear as liquid in nature, AFAIK, whereas ethane does. Methane reacts easily with other chemicals, and one of the most well known sources for it is life, since methane is a byproduct of metabolism on Earth (maybe Tim_Lou can explain this better).

After all, one of the main tasks for the Huygens probe is to find out whether the surface has liquid or not, so I am only recounting one scientist's views. There are obviously a lot of theories around.

[Tormod]

Originally posted by: Stargazer
And add to that the problem that these infrared images can't show us any of the topography of the surface, for that they need to use radar, which they have recently done for some parts of the surface.

One of the other scientists at the seminar, (I think it was Roberto Orosei of the national astrophysics institute in Rome) had put together a "dummy" topology based on the observations they had and it appears that Titan may have very deep valleys, which "could hold oceans".

But - since there as of yet are no radar altimeter data he did not even propose any dimensions. On Europa the topology is about 10 meters from the low to the high point (AFAIK) so although his illustration was intriguing it really had no scientific value apart from being food for thought.

EDIT: They DID use radar and measure the topography in another project. Here is the link:
Topography on Titan

Quote from the text: "The data show a variation in height of only about 150 meters (490 feet) over the 400-kilometer-long (250-mile-long) track, indicating that in this region Titan is remarkably flat. "

[Tormod]

I really need to point out that my background here is a bit shaky so feel free to correct me if anything seems wrong. I have a stack of papers to read here in order to write some articles for the Norwegian Space Centre and I sitll haven't got the full picture (well, will I ever...).

[Stargazer]

Originally posted by: Tormod

He thinks there is an ocean on Titan, and that it may have a depth of somewhere between 100-300 kilometers. But the dense atmosphere and the temperature would form a solid surface widh a width of 50-150 kilometers. As of now I am unable to explain why he thinks so.

Still very interesting. I didn't know that they expected a solid surface instead of just liquid.

Methane does not appear as liquid in nature, AFAIK, whereas ethane does. Methane reacts easily with other chemicals, and one of the most well known sources for it is life, since methane is a byproduct of metabolism on Earth (maybe Tim_Lou can explain this better).

But shouldn't methane be in liquid form if the temperature is low enough? Anyway, you say it reacts easily, could this mean there is no "free" methane, or at least not much, on Titan for that reason?

After all, one of the main tasks for the Huygens probe is to find out whether the surface has liquid or not, so I am only recounting one scientist's views. There are obviously a lot of theories around.

Absolutely. Perhaps we know far too little to form a certain opinion yet. Huygens should cast more light on this mystery.

EDIT: They DID use radar and measure the topography in another project. Here is the link:
Topography on Titan

Quote from the text: "The data show a variation in height of only about 150 meters (490 feet) over the 400-kilometer-long (250-mile-long) track, indicating that in this region Titan is remarkably flat. "

Both Europa and Titan are very flat then. I suppose the surface is reshaped again and again by the gravitational pull of their respective gas giant planets? I would guess that Europa is so flat because of that but also because there might be liquid water underneath the cracked ice. Could Titan be somewhat similar in that there are oceans but with sold surfaces that are melted and refrozen repeatedly? I'm just guessing here...

[Tormod]

Originally posted by: Stargazer
But shouldn't methane be in liquid form if the temperature is low enough? Anyway, you say it reacts easily, could this mean there is no "free" methane, or at least not much, on Titan for that reason?

I think there is a lot of free methane gas in the athmosphere, plus a lot is bound into the ground in different phase stages. A lot of the methane will be bound up in hydrocarbons.

The origin of the methane is a mystery, though. It is one of the reasons scientists speculate that there may be life on Mars and Titan.

Both Europa and Titan are very flat then. I suppose the surface is reshaped again and again by the gravitational pull of their respective gas giant planets? I would guess that Europa is so flat because of that but also because there might be liquid water underneath the cracked ice. Could Titan be somewhat similar in that there are oceans but with sold surfaces that are melted and refrozen repeatedly? I'm just guessing here...

Yes, both moons appear to be very flat. For Europa's part I think it is due to the ice cover breaking up and fusing back together. This is apparent from the criss-crossing lines.

On Titan I think there might be some surprises. Maybe there is solid rock on the surface? I have seen calculations which suggest oceans up to 1,000 meters deep, but they are not necessarily global. This would not yet appear on any topology map since only the surface levels have been looked at, not possible ocean depth (AFAIK).

[BlameTheEx]

Oops, Double posted.

[BlameTheEx]

Tormod

Did the guess in my last post get considered in any form?

[Tormod]

There was some mention of hot vents, but they are not likely to appear on Titan because of the way the different layers of the crust seem to be composed. The non-liquid scientist suggested that there is a layer of ice, followed by a liquid (these would be H2O or at least ethane and water), followed by what he called High Pressure ice which is heavier than water and thus sinks. After that comes the sulfate layer which forms the seafloor. Since the thickness of each layer is very thick, he did not think it was a possibility for hot vents on Titan, but he thought it was very likely on Europa.

[Stargazer]

Originally posted by: Tormod

I think there is a lot of free methane gas in the athmosphere, plus a lot is bound into the ground in different phase stages. A lot of the methane will be bound up in hydrocarbons.

The origin of the methane is a mystery, though. It is one of the reasons scientists speculate that there may be life on Mars and Titan.

Could it be that the methane on both Mars and Titan comes from underground deposits? Or would such a process have depleted the planets of most methanes already? Life is of course the most exotic theory for the presence of methane, and I really hope that is the case. It would show us that a planet doesn't have to be in the traditional "habitable zone" to harbor life.

Yes, both moons appear to be very flat. For Europa's part I think it is due to the ice cover breaking up and fusing back together. This is apparent from the criss-crossing lines.

On Titan I think there might be some surprises. Maybe there is solid rock on the surface? I have seen calculations which suggest oceans up to 1,000 meters deep, but they are not necessarily global. This would not yet appear on any topology map since only the surface levels have been looked at, not possible ocean depth (AFAIK).

I hope they are planning on doing radar mapping of most of the Titan's surface, to bring some light over that moon. I hope more missions to Saturn will follow soon... but it seems to go painfully slow, the exploration of the solar system.