[X] My Assistant

[Quintessence]

Hi I'm a new poster, and I have some questions I was wondering if someone could help me with.

1. Has anymore dome volcanoes besides Ganesa Macula been discovered? I'm guessing that there can not be just one domed volcano on the moon.

2. Have any other volcanic calderas been discovered and have they named them yet for identifaction purposes.

3. Has the the 300 mile bright Red Spot on Xanadu been identified as a hotspot. I know that they were suppose to be testing if it was a hot spot when Cassini flew over on July 2, 2006.

Thank you very much for your time

[ngunn]

Welcome, Quintessence!

This is a good topic title and I hope you get replies from volcanopele and some of the others; however it seems to be a quiet time of year here. In the meantime it may be useful to point out that discussion of individual surface features often happens just after the release of new images (especially radar). Try browsing through threads with names like 'T8 radar' - and the other T numbers. Being associated with specific orbits these threads tend to dry up so you need to look back at earlier pages 2, 3 etc. of the Titan section.

Apologies if that is all boringly obvious, but it wasn't to me when I first joined . . .

[volcanopele]

Hi I'm a new poster, and I have some questions I was wondering if someone could help me with.

1. Has anymore dome volcanoes besides Ganesa Macula been discovered? I'm guessing that there can not be just one domed volcano on the moon.

From RADAR data, none to my knowledge. There is a Ganesa-like feature in northern Fensal that ISS has observed. It is a bright circular spot with flow-like features emanating from the edges.

2. Have any other volcanic calderas been discovered and have they named them yet for identifaction purposes.

There are some caldera-like features in portions of the Ta SAR swath. If I get a chance later, I will crop them out and post them here. Not very big calderas, 20-km wide or so. There might also be one at Omacatl Macula...

3. Has the the 300 mile bright Red Spot on Xanadu been identified as a hotspot. I know that they were suppose to be testing if it was a hot spot when Cassini flew over on July 2, 2006.

I completely forgot about that!!! I talked to Jason Barnes (the main author of the Hotei Arcus paper) yesterday and he didn't bring it up so maybe they didn't see anything. RADAR radiometry data suggests that it isn't a hotspot, and that's the only constraint that I am aware of.

[Adam]

So the hotspot-thing measurement was this year? Would be nice to hear if they saw something.

[Guest_Richard Trigaux_*]

There are many circular or sub-circular features on Titan, it is not sure yet they are volcanoes. some could be meteor craters, some could be anything else we don't know. Even we don't know yet what makes the basic "mountains" on Titan. Perhaps Cassini will tell, perhaps not.

The bright feature called the smile was already discussed somewhere a moment ago. It don't seem to be a hot spot. What it is is only a matter of speculation. It could be a geological feature, it could be some hydrocarbon snow or hail left by a storm.

[nprev]

Come to that, I wouldn't be at all surprised if some of these things are low-temp analogs of Venusian coronae, especially if there are several different types of subsurface fluid mixtures in play...what little I've read of possible Titanian interior models makes the crust look like an onion, with LOTS of odd things happening in each layer.

[Guest_Richard Trigaux_*]

The most common hypothesis is that Titan soil and crust would be made of ice, floating on an ocean of water and ammonia. But nothing is sure and there could be places for other layers and other compounds.

Why a Titanian ice crust would not ressembles that of Europa? Because it is thicker? It rather ressembles that of Ganymede, with old smooth regions and white faulted young regions. But on Titan we see no collections of parallel faults in the low lands. So Titan icy crust is different of anything seen before.

Already an ammonia-water mixture would freeze as pure ice, until the mixture, enriched in ammonia, becomes an eutectic*. So the crust could contain layers and regions of pure water ice and other of water-ammonia eutectics. Or it could also contain methane chlatrates**. All these bodies have different densities, and, like water ice they can flow slowly*** with time, giving diapirs**** , mountains and other tectonic features. Many circular features on Titan, occuring alone or in clusters, could be diapirs.

This don't exclude the presence of water volcanoes, but water behaves in a very different way of silicate lavas. Silicate lavas harden little by little, giving thick flows, while water would rather erode a channel and flood low lands with a flat icy surface showing features like our arctic ice pack (also visible on Mars in the flooding plain of Athabasca valley). So it is not likely that water volcanoes ressemble our cone shaped silicate volcanoes, unless the water is muddy or something. But we could still have things like calderas.




* Eutectic: a liquid mixture with a given ratio of two chemical bodies, which freezes at a lower temperature than with any other ratio, and which gives a solid which is too a mixture with the same ratio. If the liquid is enriched with one of the two bodies, it freezes giving a solid of this pure body, and the remaining liquid is enriched with the other body, until the eutectic ratio is reached.

**chlatrates, also called methane ice, are a solid body formed of methane and water ice, which is solid at room temperature with a pressure of some bars. On Titan hot chlatrates would release water and methane.

*** solid bodies like ice or salt can slowly flow under pressure, and, in the length of geological times, behave as a fluid. Example: glaciers, salt domes.

**** diapirs are blocks of lighter rocks, such as salt, which slowly flow and rise through layers of rock, giving underground salt domes, until they reach a low density layer or the surface. On earth diapirs can give circular features on the surface of the ground, like in the Zagros montains in south Iran.

[ngunn]

Brilliant! I was going to post more here today but the posts above give a perfect synopsis - one of the things that this site does so well. There you have it: the little bit we are beginning to know and the vast amount that is still unknown, maybe even unguessed, about the geology (glaciology?) of this highly complex world. I have this fanciful picture in my head of 'glaciers' that ooze up vertically out of the interior instead of sliding down mountain-sides as terrestrial glaciers do. And then there is the atmosphere and climate too. It will keep us busy for generations.

[The Messenger]

The surface of Titan is not behaving like water we have found anywhere else, mechanically, thermally or spectroscopically. There is little if any evidence of more than trace amounts ammonia. The theroies that predicted what the surface of Titan should be need to be put on a shelf for a moment, and the physical and mechanical properties of the surface materials compared with other known, if unlikely compounds.

Deep Impact revealed a low mass comet that was high in surface silicates, clays and iron, and no more resembling an icey snowball than Mars...actually the surface of Temple 1 - a Kuiper belt object- is rather like the surface of Mars.

[Guest_Richard Trigaux_*]

...and the physical and mechanical properties of the surface materials compared with other known, if unlikely compounds.

Yes, ice don't account with what we see. Especially how ice could form the mountains seen on Titan? Some alternatives:
-solifdifyed hydrocarbons
-methane chlatrates. When heated, or slowly, they would release the methane.
-nitrides
-accumulating from slow reactions... aminoacids. (not from life of course). If so, Titan rocks would be... edible!


There are some bits known, but like puzzles where most of the parts are missing:

-Low lands would get their dark color from some organic tar falling from the upper atmosphere, and washed into low lands by some rare methane rains.
-Dunes could be formed from the same material. But, if so, why, if Huygens landed into a dark region, there was no dunes?
-Why there was pebbles in Huygens landing point, where we are far from any mountains? Understand that, in earth's deserts, rare but violent rains form large flood plains and alluvion fans. But, usually, these alluvions are sand or clays, not pebbles. The difference with Titan would come from the fact that, On earth, pebbles are about three times denser than the water. But on Titan, they could be of about the same density, so that alluvions would be larger and would travel mucht farther. At a pinch, some titanian rocks would have a lower density than the fluid!! If so pebbles would rather float on streams!
-Or the rounding of the stones could come from dissolution (for instance from an hydrocarbon ice into a liquid hydrocarbon like methane). Or on the countrary from accumulation around a seed...

[tty]

Pebbly alluvial deposits are quite common on Earth, for example in braided river deposits. Actually the pebbly deposit at the Huygens landing point looks liquid-deposited to me.

tty

[Guest_Richard Trigaux_*]

Pebbly alluvial deposits are quite common on Earth, for example in braided river deposits. Actually the pebbly deposit at the Huygens landing point looks liquid-deposited to me.

tty

The Huygens landing point don't seem to be a river bed.

On Earth, there are flood plains covered with pebbles, you can see one at Google Earth 31°35'N 2°11'W eye altitude 8kms (24000 feets. Yes there is an option in Google Earth to have metrics. Menu Tools>options>Wiew, hurry up the old timer brits! ). This place is covered with dark blocks (probably sandstone) from the mountains at right, ranging about 10cm to 20cm in size. They were removed to make the two tracks (a bit like in Nazca) letting see a clearer ground. I think that only a very violent rain event could flood this place with enough water to move 20cm blocks over distances of kilometres, not only into a small river bed, but all over a 30-50kms wide flood plain! On this example, this is because there is a tall mountain just nearby, and a bit of a slope (the little oasis at the foot of the mountains, where the two tracks join, is at 5kms and 100m higher than the wadi at the left, that makes a 2% slope)

But the Huygens site is not at the foot of a tall mountain, at best hills of 10-20m high (not visible in the camera field, but seen during descent) That makes much less than a 2% slope....

I too think that the most likely hypothesis is still that these pebbles were transported by a liquid flood, but there is some parameter which was very different of Earth's. The difference of density may explain that such large pebbles can be found in a flood plain so far from any tall mountain. And they were transported, perhaps million years ago, at the occasion of a very violent rain. More recent rains may have washed the dark tar which falls from the sky.

[Olvegg]

But the Huygens site is not at the foot of a tall mountain, at best hills of 10-20m high (not visible in the camera field, but seen during descent) That makes much less than a 2% slope....

Stereopairs of Huygens images show the height differencies of 150-200 m, and rather steep slopes:
http://www.lpl.arizona.edu/~kholso/multime...s_arcmap_8A.avi
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2089.pdf

The difference of densities (1:2) is indeed smaller than on Earth. Moreover, the gravity is very small (though I'm not sure what effect it has on pebbles transportation).

[Guest_Richard Trigaux_*]

Thanks, alan. I had missed that. Well, the context does look promising. Two long channels cutting through a mottled area, opening into a smooth flat area. Could be alluvial. This really makes you want a good DEM, though! The next mission just has to give us global SAR and topography...

Phil

The next mission should be an orbiter, to give us clear radar coverage, together with a baloon. It would be relatively simple to do if we don't attempt landing, and a baloon would provide us with much clearer images and unbiased spectrums, eventually a radar altimetre or stereo views, to clearly discriminate land forms from land colours. It could identify places of interest for further landings, for instance cryovolcanoes, if there are. Recent water flows are the best place to study inner Titan chemistry and eventual life forms.

[djellison]

It would be relatively simple to do if we don't attempt landing,

There is nothing simple about flying an orbiter to Titan and deploying a balloon into its atmosphere.

Doug