Probable lakes on Titan

tom_hobbes · Nov 17, 2006

It gets far more exotic than that. http://www.astrobio.net/news/article352.html <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

JonClarke · Nov 17, 2006

Venus appears to have lead sulphide snow . Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

mikeemmert · Nov 17, 2006

Hi, silylene, sorry I'm late getting back. Some of the intervening threads have mentioned that pressure raises boiling points and I assume this is true for methane, also. Isn't the surface pressure on Titan higher than atmospheric pressure? Notice also that the lakes (if that's what they are) are located in the winter hemisphere, currently the northern one. If bodies of liquid are seasonal, then that's where they'll be. If they're diurnal, then Huygens landed at the wrong time of day. Remember, Titan's day is 15.94 times our day. On the other hand, there's a good possiblility that the camera wouldn't work in lighting conditions suitable for rainy weather there. Does anybody know what (local) time of day Huygens landed? If it was late afternoon, well, that's what happened to the lakes. I'm certainly not a radar expert, but I do know that the microwaves from my oven go right through plastic like it's not even there. The windows of police radars and radar domes also are hydrocarbon plastics. This might make lakes very hard to detect. OK, you're the board's chief expert in this subject; what compounds do disolve in methane at these temperatures? How about cyanide, methyl cyanide, acetylene, and diacetylene? How about silylene? It's hard to imagine a source of silicon on Titan's surface, though...I know that's a silly question but I'm actually trying to get you to think ouside the box about what compounds there could be disolved in any lakes out there, ranging from neopentane to n-heptane. There are a lot of features from the Huygens photos that look to me like they were carved by a running fluid. Of course, that's true of Mars, too, and it now appears those features are billions of years old.

yevaud · Nov 17, 2006

Just an aside, but I'd be of the opinion that a Methane lake would still provide a very "bright" Radar return. Not to mention, liquid Methane would also tend to stand out Radiometrically, in certain bands. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

yevaud · Nov 17, 2006

Addendum: Astrobio says no to that, although my gut feeling as a former Radar tech is that's still wrong. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

yevaud · Nov 17, 2006

Ah, I see. On the one hand, they don't get a good Radar return from the "Methane Lakes." On the other hand, they do obtain other Radiometric data that does suggest at least a reasonably different composition for those areas. Such as a 3k increased Brightness/Temperature. Edit: (been doing some research) one possible answer for the combination of returns across all measuered bands is a Hydrocarbon. Hmm. Well, something odd is there at any rate. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

tom_hobbes · Nov 17, 2006

Crikey, snowmen are hot on venus... <div class="Discussion_UserSignature"> I wish I could remember But my selective memory Won't let me - Mark Oliver Everett </div>

JonClarke · Nov 17, 2006

Methane has strong IR absorption bands, so their composition should be detected using VIMS. Liquids generally offer specular reflections as well when the angle is right, so far this has not been reported from Cassini data, although some have been found in terrestrial studies using the Arecibo radio telescope. On current evidence I would say that there is 100% probability of a methane cycle on Titan and 80% probability that we are in fact seeing methane lakes. Discovering specular reflections from the putative lakes would push that probability past 90%. IMHO of course. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

yevaud · Nov 17, 2006

Understood. The Brightness Temperature shows a clear 3k difference, and that's a high emissivity. As I'd said, one of the possible interpretations is something composed of liquid Hydrocarbons. I see part of the problem with the onboard Radar. If you're trying to puch through the optical depth of Titan's atmosphere, yet detect something largely comprised of the same species, discriminating between them is a real Bear. Essentially the only difference is the reflective change from a gasseous to a liquid form (being the 3k difference measured). Glad they have a competent suite onboard, to image the lakes in other bands also. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Nov 17, 2006

And heavy <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

brellis · Nov 17, 2006

Crikey, snowmen are hot on venus... so are the gals! <img src="/images/icons/wink.gif" /> As to the Huygens landing site, was any detail obtained? Were they able to determine the consistency of the soil? Was it like sand or mud, or dried clay? I'm probably several pages behind here, but how does the cryo-volcano explanation for the methane in the atmosphere relate to the new images? <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

JonClarke · Nov 17, 2006

You would presumably look for two reflections, a specular refection from the liquid-gas interface and a diffuse reflection from the solid-liquid one. A bit like using airborne radar or satellite radar to map beneath ice caps where there is one reflection from the ice surface and another from the bedrock surface. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

yevaud · Nov 17, 2006

That was part of the criteria for the return being a liquid hydrocarbon: subsurface reflections. Do you see these as seasonal storms? That is, the lakes condense and then evaporate, depending on one of Titan's "seasons?" Just curious. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Nov 17, 2006

It certainly is possible. If these features are lakes then perhaps some are permanent and others ephemeral. Hopefully Cassini lasts long enough for us to see how stable these feature are. Ephemeral lakes would explain why soem radar studies from Earth have found specular reflections and others not. In the equitorial areas I think the presence of methane rain and liquid methane in the soil as detected by Huygens, combined with the dendritic channels, means that methane flash flooding is a certainty. The smooth dark lowlands would be be tholin pans, analogous to salt and clay pans on Earth. Note that in the post landing image taken by Huygens we see rounded pebbles, very low relief channels, and sdiment tails behind pebbles. Very similar to what you get on a flood out onto a salt or clay pan on Earth. Of course we see nice looking dunes on Titan too, so it is possible that the sediment tails are due to wind. But it certainly intriguing. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

yevaud · Nov 17, 2006

Interesting indeed, and thank you. Those terrain features aren't produced by nothing, after all, and are a good indicator of sometimes liquid Methane. Or so it seems. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Nov 17, 2006

The meterology of a world where are large fraction of the atmosphere could seasonally condense is going to be interesting. The evocative but inaccurate term methane monsoon has been coined to describe it, the first use was by Arthur Clarke in his 1975 novel "Imperial Earth". Something similar happens on Mars where each winter a large fraction of the atmosphere freezes as snow on one or the other of the polar caps. It's a major driver in atmospheric circulation. Certainly the big linear dunes on Titan - the "catch scratches" - point to episodic, reversing wind directions strong enough to transport sand particles. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

enigma10 · Nov 17, 2006

Talk about missing a point. <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

yevaud · Nov 17, 2006

I can appreciate what Clarke meant. With such a tight temperature range for remaining a liquid, an abrupt but even modest temperature increase would cause a sudden evaporation and hence a "high-pressure weather front" moving outwards. Vigorously. Yow. Of course, this as well might explain all of the surface features indicative of sudden liquid runoff. As the Methane streams outwards from the sudden hotspot hence evaporation-derived high-pressure front, it will of course move into relatively cool areas, where a sudden torrential rain of liquid Methane would occur. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Nov 17, 2006

In the book, as I recall (can't find my copy), some of the early expeditions come to grief because of it. It is a fascinating book for a whole range of reasons, and, even though dated in part, is still perhaps the most detailed treatment of the issues of how a settlement on Titan might work and how it could be justified economically. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

silylene old · Nov 18, 2006

Mike, you are right that the higher surface pressure on Titan will extend the methane liquid range. The kinds of compounds that dissolve into cold, liquid methane would be non-polar organics, especially hydrocarbons. I would think that methyl cyanide, acetylene and diacetylene would be soluble. HCN would have sparing solubility. I do agree that the features do look like lakes and that the channels do look as if they were carved by a liquid. And I agree a location near the pole of Titan would improve the chance for liquid to exist. I am just waiting for one more independent supporting piece of data, such as an unequivocal specular reflection, before I jump onto the liquid lake bandwagon. Until then, I will assume the lakebeds are ephemeral and likely dry. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center">- - - - - - - - - - - - - - - - - - - - - - </div><div class="Discussion_UserSignature" align="center">I really, really, really miss the "first unread post" function. </div> </div>

mikeemmert · Nov 18, 2006

<blockquote>In reply to:<hr />I am just waiting for one more independent supporting piece of data<hr /></blockquote>As is everybody else, apparently, ranging from extreme skeptics such as stevehw33 to extreme optimists such as myself. Everybody wants a new rover with greater capabilities. And, I would like to add, a Titan orbiter, with a new radar calibrated according to the findings of Cassini, with a newly designed nuclear reactor for more powerful transmissions which could study the atmosphere better and send commands to the Enceladus rover, tethered to the surface with an optic fiber cable as it dives into the mysterious waters of the geysers found there. In the sober debates about the gigabucks spent on future missions, I would think the Saturn system has proven to be more interesting than Jupiter. Thus a new Saturn probe should get priority over JIMO. Europa is very interesting, but there is no evidence that Europa's postulated ocean is connected anywhere or in any way to the surface. It might be possible that an Enceladus swimmer would not have to melt it's way through kilometers of rock-hard ice. Life is more likely at Enceladus than Titan. But I haven't given up on finding life in Titanian lakes. There might be liquids and I think there are. There are certainly high-energy compounds, acetylene and others, in the atmosphere for Titanians to eat; the evidence for this ought to meet even stevehw33's standards. This is part of a larger question. Let me illustrate by posing a related smaller question: Given Earthlike conditions, will any life which arises always utilize chlorophyll as the energy-gathering compound? Or did chorophyll-using life win out here on Earth against other compounds by sheer luck of the draw? There are an enormous number of light sensitive compounds. Who would have thought that silicon would have won out in the photographic industry? I bet Mr. Daguerre wo

3488 · Nov 22, 2006

Hi all. I understand your point mikeemmert. Enceladus IMO must be explored further, whether or not the Saturn system is MORE interesting than the Jupiter one is open to question. If you were to take Titan, Enceladus, Iapetus & Phoebe out (Phoebe because it may be a Kuiper Belt escapee & may reveal much about the Sun's outermost kingdom, until New Horizons arrive at the Pluto system), the Saturn system of moons would be dull boring cratered ice rock balls (such as Rhea, Tethys & Mimas in particular). Even Hyperion, although visually interesting, is still a cratered tumbling lump of unevolved dirty ice. The Jupiter system has four moons, large enough to be planets in their own right, Io with its impressive active geology, Europa an enigmatic object with a possible sub surface ocean, Ganymede, highly differentiated, varied surface, with its own magnetosphere, self generated (the only moon in the solar system known to have one) & Callisto just simply being such an odd ball (with potentially a sub surface ocean). To me, the Jupiter system is more interesting, BUT the Saturn one being so different. To me with the Saturn system, any extended mission with Cassini should concentrate on Titan, Enceladus & Iapetus as well as Saturn itself. Leave the other moons out, unless of course there is a chance encounter or in the mean time something else crops up with them. It is worth remembering that Galileo had a crippled High Gain Antenna, whereas Cassini could never have that problem, so the amount of information returned is very much higher with Cassini. Just my own opinion. BTW, is there any info about: 1). The possible internal structure of Titan (is it differentiated like Ganymede, or homogenous like Callisto, is there evidence of a molten core)? 2). Is there any evidence of Titanian ice ages (Nitrogen / Methane glaciers, atmospheric collapse in the distant past when the Sun w <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

ldyaidan · Nov 22, 2006

Jon, Thanks for all the great info! I always learn a lot from your posts. I appreciate your patience, and explaining things in laymans terms! Keep up the great work! Rae

JonClarke · Nov 22, 2006

Hi Andrew Thought provoking questions as always. My make on them would be: 1) The young surface (few impact craters), high atmospheric radiogenic argo, and possible signs of cryovolcanism would suggest that the interior is differentiated. I imagine that orbital dynamics calculations from both Titan's orbit and peturbations of Cassini would ell useful information about distribution of mass inside Titan and thus differentiation. 2) Interesting possibility. Perhaps not ice ages, but pluvial epochs are a possibility if what appear to be dry lake beds are just that. But they could also be seasonal as well. 3). Not sure. I have seen some figures suggesting it is quite low - less than 10 degrees. That was based on modelling post Voyager. This would be expected given the very dense atmosphere would be very effect at heat transfer, as with Venus. Cheers Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

mikeemmert · Nov 22, 2006

<blockquote>In reply to:<hr />To me, the Jupiter system is more interesting<hr /></blockquote>Ah, that's a tough call...I knew I'd get in trouble over this...I wish Congress would pony up some more money so that these kinds of conflicts won't ariise. Better yet, if we could get other countries, like China and India and Mozambique and, yes, Great Britain, to pony up some real cash instead of token sums, we could do both. Kumbaya?<blockquote>In reply to:<hr />If you were to take Titan, Enceladus, Iapetus & Phoebe out (Phoebe because it may be a Kuiper Belt escapee & may reveal much about the Sun's outermost kingdom, until New Horizons arrive at the Pluto system), the Saturn system of moons would be dull boring cratered ice rock balls (such as Rhea, Tethys & Mimas in particular).<hr /></blockquote>However, Titan, Hyperion, Iapetus, and Phoebe are in the picture.<blockquote>In reply to:<hr />Even Hyperion, although visually interesting, is still a cratered tumbling lump of unevolved dirty ice.<hr /></blockquote>Here's the caption on the image page (not the main page) of the backside of Hyperion for the Widipedia article on Hyperion: "Original caption: Unlike most of the dull grey moons in the Solar System, Hyperion's color is a rosy tan, as this view shows. The origin of the moon's unusual hue is not known. Some scientists suspect the color comes from falling debris from moons farther out. A similar origin has been suggested for the dark reddish material on Saturn's moon Iapetus. Images taken using red, green and blue spectral filters were combined to create this natural color view. The images were taken in visible light with the Cassini spacecraft narrow-angle camera on June 28, 2006 at a distance of approximately 291,000 kilometers (181,000 miles) from Hyperion. Image scale is 2 kilometers (1 mile) per pixel

Probable lakes on Titan

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