Probable lakes on Titan

JonClarke · Nov 12, 2006

I know these were mentioned in the Cassini thread on M&L but.... Amazing! http://photojournal.jpl.nasa.gov/catalog/PIA01942 http://photojournal.jpl.nasa.gov/catalog/PIA01943 The detail even at this coarse resolution is remarkably similar to terrestrial shorelines and coastal geomorphology. I can see drowned estuaries, possible spits and beaches, sub "aqueous" bars and channels, as well as ellipical lakes suggesting wind-driven cycloidal circulation. 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 12, 2006

Jon, your observations do look like that! Question: Can the Cassini radar actually "see" sub-"aqueous" bars and channels, or is it limited to surface-only reflection? How far can the radar penetrate liquid ethane/propane, and if it did, how would the reflected signal look to the detector and software systems? I sure would like to know more about the technical specifications! If the Cassini radar cannot see subsurface lake-bottom landforms, this would imply that the lake is all dried up, and that the lake floor bottom is very smooth and specular. <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>

centsworth_II · Nov 12, 2006

"...I can see drowned estuaries, possible spits and beaches, sub 'aqueous' bars and channels, as well as ellipical lakes..." You are spoiling for a slapdown from Stevehw33. Let's hope he's more civil with you than he is with the run-of-the-mill poster. <div class="Discussion_UserSignature"> </div>

JonClarke · Nov 12, 2006

If these very dark features are liquid, then the radar is certainly seeing through it. Rdar can't see through liquid water, but I believe it may be able to see throuh liquid methane, to some extent. Someinput from someone who unerstands radio progogation through liquids much better than I do (not hard!) would be appreciated If these features are not stand liquid, then I we have to say that this is an area that had liquid in the geologically very recent past. I can't think of anything else that would generate such patterns. 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 13, 2006

<blockquote>In reply to:<hr />The problem is that of the false analogy. Taking liquid water events at or above the melting point of water and then tranferring such well defined events & terrminologies to the unknown and not at all defined surface of Titan at Minus what, 180 C? And with no water, and a messy mixture of methane + GOK, a heavy nitrogen atmosphere & occ. comet impacts and some infalling mass from the rings not to mention an occ. . burp of ice crystals from Enceladus..... <hr /></blockquote> Water, being H2O, was never mentioned, outside of a comparison to radar penitration. I believe liquid hydrocarbons was noted as the possible liquid in the link.Would that be a false analogy using such a term then? <img src="/images/icons/smile.gif" /> But of course, the absolutism of what is really there on the surface could never be known without extensive surface landing probes, like on mars. <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

JonClarke · Nov 13, 2006

Steve, you don’t make any sense at all. The problem is that of the false analogy. Taking liquid water events at or above the melting point of water and then tranferring such well defined events & terrminologies to the unknown and not at all defined surface of Titan at Minus what, 180 C? And with no water, and a messy mixture of methane + GOK, a heavy nitrogen atmosphere & occ. comet impacts and some infalling mass from the rings not to mention an occ. . burp of ice crystals from Enceladus..... First of all the surface of Titan is not unknown. We know that the surface is solid, is composed of bedrock and loose materials and a wide range of landforms, some familiar, some not. Second, there is water on Titan, most of it is solid. Heat flow and density data makes it almost certain that some form of liquid water occurs as depth. What are those surface features? Well, most will wait for Cassini 2, or 3 and 4 and some more long lasting probes to find out more. & at LEAST one, well observed, high velocity, thermolytic, impact event, which would likely tell us more in 30' than ALL those lo res images.... You don’t seem to understand how science works. You formulate hypotheses on the data to hand and then test those against new observations. Some, perhaps most. will be proved wrong, others will withstand criticism. Nobody is doing to wait until your imaginary Cassini 2, 3, or 4 to start this process. Scientists always formulate and test hypotheses from the moment we start collecting data which in the case of planetary science starts with telescopic observations. Do you really think that the mission scientists are going to tell the politicians, bureaucrats, and taxpayers of the US and Europe that after more than a billion dollars and Euros invested that they don’t have any conclusions to draw? You also don’t seem to understand the wealth of data that Cassini and Huygens are generat <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 13, 2006

Radar can't see through liquid water, but I believe it may be able to see through liquid methane, to some extent. Some input from someone who unerstands radio progagation through liquids much better than I do (not hard!) would be appreciated Agreed, Jon. I think this information is key to understanding whether these lakebeds are currently filled with liquid now, or whether they are now 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>

dragon04 · Nov 13, 2006

Given the atmospheric pressure on Titan, and the surface temperatures, can methane exist in liquid form? <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

ellesbells · Nov 13, 2006

i watched a programme on titan, and that due to the temperatures rain would fall but it would evaporate before it touched the ground! sounds cool... there is sure to be life on that moon?!

MeteorWayne · Nov 13, 2006

Except for the temperature. Cold that intense is a real challenge for life, which functions on chemical reactions. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

CalliArcale · Nov 13, 2006

<blockquote>In reply to:<hr />Given the atmospheric pressure on Titan, and the surface temperatures, can methane exist in liquid form?<hr /></blockquote> In theory, yes, although it should evaporate, which means that any "lakes" of it can only be either short-lived features or must be replenished. Interestingly, the lake-like features observed on Titan so far seem concentrated on the "winter" side of Titan. The Cassini mission won't last long enough to see if lake-like features start to appear on the other side of Titan as the seasons shift (Titan's seasons are as long as Saturn's, and Saturn's orbital period is a bit over 30 Earth years). This could be because the lakes only persist as long as there is methane rain to fill them up; it might only be cold enough to allow liquid methane to precipitate during the winter. But it'll take more data to be sure of that. It's one of several plausible theories. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

brellis · Nov 13, 2006

(Titan's seasons are as long as Saturn's, and Saturn's orbital period is a bit over 30 Earth years) Wouldn't this be a reason to leave Cassini in some kind of orbit following Titan around Saturn? I fail to understand why we should send Cassini crashing into Saturn while there is still fuel left in her. I'd favor milking every last piece of data over the implausible argument that after more than a decade in space, Cassini somehow contains microbes that could contaminate the environment of a moon out there. <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

JonClarke · Nov 13, 2006

With respect to liquid methane on Titan you wrote: it should evaporate, which means that any "lakes" of it can only be either short-lived features or must be replenished. This is also true of water lakes on Earth. Interestingly, the lake-like features observed on Titan so far seem concentrated on the "winter" side of Titan. The Cassini mission won't last long enough to see if lake-like features start to appear on the other side of Titan as the seasons shift (Titan's seasons are as long as Saturn's, and Saturn's orbital period is a bit over 30 Earth years). This could be because the lakes only persist as long as there is methane rain to fill them up; it might only be cold enough to allow liquid methane to precipitate during the winter. While Cassini won't last a full Saturn year, hopefully it will last long enough to image seasonal changes on Titan. 7-8 years of operation should do it. 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 13, 2006

Huygens might have landed in the right place, but the wrong time! I'm sure this must have had something to do with being able to photograph the surface as it descended. Next time we'll know better and land on the pole that's having a winter. I used to live in New Mexico, where all but a few bodies of water are temporary. The Huygens landing site looked to me like it might be an analogue of a dry lakebed.

CalliArcale · Nov 13, 2006

<blockquote>In reply to:<hr />This is also true of water lakes on Earth. <hr /></blockquote> Yep. It would be interesting to discover if there's a "methane cycle" on Titan which is in any way comparable to the water cycle here on Earth, which of course replenishes our lakes. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

mithridates · Nov 14, 2006

<blockquote>In reply to:<hr />I see. Has there been ANY confirming observation of such precipitation? Has anyone actually observed this 'rain' visually or by an instrument which would clearly show it? No. Has there been any confirmation of this deposition by watching this deposition as it occurs?? No. Has there been ANY on site analysis of these 'dark' materials, which confirms they are organic, and a good compositional analysis? No. Those are, therefore simply hypotheses, consistent with what has been seen, but NOT confirmed. <hr /></blockquote> You're grasping at straws here. <div class="Discussion_UserSignature"> ----- http://mithridates.blogspot.com </div>

silylene old · Nov 14, 2006

This is why the surface of an ice cube is ZERO C. The surface of the Titan "methane cube" is also MINUS 180 C. but in this case the reverse is true. The ice cube melts due to atmospheric transfer of heat to to the cube. the Interior of the cube is colder, or it'd be slush. Actually, you don't know this. The temperature of the surface of an ice cube is a maximumof 0 C. Actually the temp of the surface of that cube can be anywhere between -273.15C and 0 C, and the water would still be a solid (assuming 1 atm of pressure). (and yes, I am ignoring the unusual surface phase properties of the top 5 nm of a solid - a subject for another thread). In a similar manner, the temperature of the surface of a CH4 "cube" is somewhere between -273.15C and -180C (at 1 atm pressure). Actually, it is highly unlikely that the entire surface of Titan is at thermal equilibrium with the liquid/solid phase transition of CH4, as (I think) you are arguing. There will be cooler locations, and there will be warmer locations on the surface. This will occur because the heat sources (sun and endogenous subsurface) is not evenly distributed across the surface. In addition, the atmospheric circulation is not perfectly efficient in thermal mixing (causing weather). Consider that the Earth's surface is covered by 70% liquid water and about 8% solid water. Despite this huge thermal sink of water, the Earth's surface temperature has not settled to arrive at perfect thermal equilibirium with the temperature that corresponds to the freezing/thawing of water (0 C). The average surface temp is close - about 15C, IIRC. However, there are large variations in local surface temperature from that mean, ranging from -89C in Antarctica (cool enough to freeze CO2) to 54C in Death Valley. I would expect the same for Titan; that there will be significant local and seas <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>

JonClarke · Nov 15, 2006

Once again you completely miss the point. Actually we know a LOT more about the surface of the moon than we do Titan. We know a lOT more about the surface even of comets than we do Titan. It's almost unknown, as we have ONE spot where Huygens landed. The composition of the rest of it is all but TOTALLY unknown. You have shifted the goal posts. From knowing nothing about Titan you have moved to us knowing less about Titan than we know about the Moon. This is called shifting the goal posts. Of course we know a lot more about the Moon than we do about Titan. But this is irrelevant. Just because we know more about the Moon than Titan does not mean we know nothing about Titan. We know quite a bit about Titan thanks to centuries of ground-based observations at optical, UV, IR and radio wavelengths, older probes like Pioneer 10, and Voyager 1 and 2, as well as Cassini-Huygens. Or do you deny we learned anything from these missions and observations? Or do you have some compositional detail on a cm. by cm. basis somewhere there, which was taken by a surface probe? Cm scale surface information is completely irrelevant to knowing whether or not methane can condense on the surface of Titan. For that we need to know the phase relationships, which we can get from spectroscopy, radio occultation studies, and direct measurement from the Huygens probe, supported by radar studies of the surface to see whether or there are features that occur within the phase space of liquid methane that have the right characteristics. Do you have drillings from the interior of these features? NO. Drilling is irrelevant to the phase state of methane on the surface. The surface composition of Titan, which is what I was referring to, is totally unknown, except for that site where Huygens landed and did a partial, short analysis of. Wrong. There is IR spectroscopy using the VIMS instr <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>

JonClarke · Nov 15, 2006

Has there been ANY confirming observation of such precipitation? Has anyone actually observed this 'rain' visually or by an instrument which would clearly show it? No. Yes Methane storms on Saturn's moon Titan R. Hueso and A. Sánchez-Lavega Nature 442, 428-431 (27 July 2006) “The presence of dry fluvial river channels and the intense cloud activity in the south pole of Titan over the past few years suggest the presence of methane rain. The nitrogen atmosphere of Titan therefore appears to support a methane meteorological cycle that sculptures the surface and controls its properties. Titan and Earth are the only worlds in the Solar System where rain reaches the surface, although the atmospheric cycles of water and methane are expected to be very different. Here we report three-dimensional dynamical calculations showing that severe methane convective storms accompanied by intense precipitation may occur in Titan under the right environmental conditions. The strongest storms grow when the methane relative humidity in the middle troposphere is above 80 per cent, producing updrafts with maximum velocities of 20 m s-1, able to reach altitudes of 30 km before dissipating in 5-8 h. Raindrops of 1-5 mm in radius produce precipitation rainfalls on the surface as high as 110 kg m-2 and are comparable to flash flood events on Earth.” Nature 442, 428-431 (27 July 2006) Methane drizzle on Titan Tetsuya Tokano, Christopher P. McKay, Fritz M. Neubauer, Sushil K. Atreya, Francesca Ferri, Marcello Fulchignon and Hasso B. Niemann Nature 442, 432-435 (27 July 2006) “Saturn's moon Titan shows landscapes with fluvial features suggestive of hydrology based on liquid methane. Recent efforts in understanding Titan's methane hydrological cycle have focused on occasional cloud outbursts near the south pole or cloud streaks at southern mid-latitudes and the mechanisms o <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>

JonClarke · Nov 15, 2006

I do think the biggest argument against Titan methane lakes is that the delta-T between the melting point and the boiling point of CH4 is only about 21C (at 1 atm), and that the heat of vaporization of CH4 is small. 21C is a very narrow range. For water, it is 100C. In addition, the heat of vaporization of CH4 is 577 kJ/kg; water is 2260kJ/kg. This means it takes 4x less heat to evaporate methane from the liquid, compoared to steam from water. It's not an argument against the presence of methane, simply an observation that points out some of the pecularities of Titanian "methanology" (c.f. "hydrology"). The "methane monsoon" is one posulated result. A similar situation exists on Mars, where, when present, the boiling and freezing point of pure water are less than 20 degrees apart, even in the lowest parts of the Martian surface. This is why I have some doubts whether the lakes actually currently contain liquid. I suspect they are dry lakebeds. That is why I asked Jon if he knew if the Cassini radar is capable of penetrating hundreds(?) of meters of liquid CH4 to accurately image subsurface features. If the answer is "no", then we know the lake is dry. If the answer is "yes", I don't think we can know one way or the other if liquid is present (unless there is some unqiue specular microwave reflection data which is impossible to happen with a smooth solid surface). if the lakes are episodically dry then they are likely to be both shallow Depending on composition, radar can penetrate quite a way into liquid methane. See http://www.planetary.org/blog/article/00000733 "The liquid that carved the channels appears to have collected in radar-dark lakes. Several styles of lakes have been identified. Type 1 lakes have discrete boundaries and in a few instances, we may be seeing through the liquid and sensing the lake bottom. These <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 15, 2006

Jon, Thanks for the information on radar penetration. It does make me feel more comfortable with the possibility that the lakes may be currently filled with liquid. It's not an argument against the presence of methane, simply an observation that points out some of the pecularities of Titanian "methanology" (c.f. "hydrology"). The "methane monsoon" is one posulated result. A similar situation exists on Mars, where, when present, the boiling and freezing point of pure water are less than 20 degrees apart, even in the lowest parts of the Martian surface. Agreed Jon, and a very excellent analogy. On Mars (currently), potential water lakes are thought to be ephemeral. I do think the same may be true on Titan (methane lakes). Another thing to consider is that it is a whole lot easier to depress the freezing point of water by dissolving solutes into it, than it is to depress the freezing point of methane in a similar manner. Thus, water on Mars (in practice) might have a much wider liquid range than methane on Titan. (for two reasons: colligative properties such as fpd are very influenced by ionic solutes, and CH4 won't dissolve ionic salts; and not many liquid cosolvents have a lower bp than CH4 which limits the maximum fp depression possible by liquid-liquid cosolvency.) <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>

CalliArcale · Nov 15, 2006

stevehw33, would it be safe to say that nothing that can be done in the next ten years will satisfy your standards with regards to discussing possibilities about Titan? (It is so unlikely as to be laughable that a specifically targetted probe could be sent there by 2016, in my opinion, so we are limited to what Cassini can tell us, and apparently that does not satisfy you.) Does that mean that people may not investigate what data *is* available? You have a history of intentionally destroying threads about the possibliity of liquids on the surface of Titan (and indeed liquids anywhere other than Earth). You do not have to believe that there could be liquids anywhere else. You are entitled to your view. But others are entitled to their views too, and are entitled to discuss them. You are denying them that possibility and creating a lot of bad blood in the process. Please, if you have nothing new to add to this subject, just move on and let people discuss it in peace. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

enigma10 · Nov 15, 2006

Steve. By your standards, we would never know what the sun is made of. <div class="Discussion_UserSignature"> "An organism at war with itself is a doomed organism." - Carl Sagan </div>

MeteorWayne · Nov 15, 2006

Good point. All the drill bits melted. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

mithridates · Nov 15, 2006

Zuh? I made the claim for what? Looks like you're confusing me with someone else. Unfortunately though it is you that is making wild claims here, that one must directly witness a phenomenon in order to know that it happened. I don't think you realize that the burden of proof is on you in this area. Considering you were the one that thought the atmosphere of Venus would be *hotter* dozens of km above the surface than the surface itself in spite of hard data from Soviet balloons showing this not to be so, you'll have to forgive me if I don't take your opinion on Titan all that seriously either. <blockquote>In reply to:<hr />And that's the difference between someone who has been trained in the sciences, vs. someone who has not been well trained.<hr /></blockquote> How is it so difficult to extrapolate the surface of Titan from the available data, yet somehow magically possible to extrapolate the scientific training or lack thereof of an individual from a few posts on a board? Inquiring minds want to know. <div class="Discussion_UserSignature"> ----- http://mithridates.blogspot.com </div>

Probable lakes on Titan

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