Enceladus, the Europa of Saturn

mikeemmert · Mar 11, 2006

Thanks for all the papers. All hypotheses should go on the table at this point. So far, I have read only the link in the post I'm replying to, about the diapirs. Fortunately, Scientific American had a great article on diapirs a few years back, so I'm not totally unfamiliar with them. This was about Earth diapirs, of course. One figure they used that struck me is that they assumed a density for the ice of 950 kg/m^3. Water has a density of 1000 kg/m^3, so it would sink through such ice. This leads me to believe that the ocean of Enceladus must be very close to the surface for water to make it up through those cracks. If diapirs were compositional in nature, then they would have reached equilibrium postitions a long time ago. Afterwards, such motion would stop. So we wouldn't see it in the present day. Earth diapirs are mostly powered by radioactive elements in the core. They are essentially convection currents through a semiplastic solid. They are not much affected by the Earths' much faster rotation because the forces generated are swamped by viscuous forces. There is plenty of uranium and thorium to account for the heating of the Earth. Not so on Enceladus. And as for aluminum-26, that was gone a long time ago. Formation of diapirs requires a heat source. It's unlikely that it would be a heat source. For any diapirs to show up in the silicate core would require much higher temperatures than what could be expected. After all, the core is water-cooled.

efron_24 · Mar 11, 2006

When searching for info online, I found this article http://www.etext.org/Zines/Quanta/life.html from 1990 in which they state that Voyager II already found some water geisers. .. amazing <div class="Discussion_UserSignature"> </div>

efron_24 · Mar 11, 2006

And hup... a question. Is it possible that Saturn is slowly ripping the poor moon apart ??? Do we know if Enceladus is being pulled towards Saturn and if so.. in the (near) future it becomes a complete ring ? The reason I ask is that I can imagine that many years of ice geisers means that the moon is getting smaller and smaller (anyway)... The plumes go higher than the moon's own size and although there seems to be some snowfall (wow.. !!!! i can't wait for the first artists to render some amazing peaces of Art... Standing there seeing plumes of ice over a (nearby) horizon shoot up HIGH into a black (?) sky... but Not only blackness... Imagine !!!!!! : 'Rainbows' beyond believe !!!!!! The rings of Saturn visual from one side of the moon and when walking a bit further you would see colorfull Saturn jump into vision.. and all around you.. snowflocks !!! That must be a WOW place to be (with Mars, Titan, Triton and Io) One can only be jealouse on those being born today. They will see so much more . It would be a wise thing if all wars stopped today, and the money spend on wars went into space exploiration.. as we got to see it all ! <div class="Discussion_UserSignature"> </div>

mikeemmert · Mar 11, 2006

Thanks. Interesting, first I heard of it was this thread a while back (old thread). The author of the link is a pretty good writer.

chebby · Mar 12, 2006

Aha, I knew there had to be a big fat thread on Enceladus on SDC. For some reason I though it would be in M&L or FS. Nice job hiding it, people!

brellis · Mar 13, 2006

thanks to all for a great thread. i'm turning Enceladusian! <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

mikeemmert · Mar 14, 2006

Good evening, borman. <blockquote>In reply to:<hr />The reason to look for constraints is to limit whether there can be diapir motion through various ices. This should not be a problem for a big moon like Europa, but it might be a challenge for tiny Enceladus. We are so early in the data aspect that it is useful to try to eliminate a large multitude of guesses as well as try to get a better guess started.<hr /></blockquote>I would agree that it would be good to start eliminating some guesses. My guess is that Enceladus has a global ocean and that the crust is not very thick. Water is denser than ice and would sink though ice. To test this hypothesis, pour yourself a glass of water and put ice in it. I don't see how water could make a narrow path to the surface. Also, the surface of Enceladus is slightly warmer than can be accounted for by solar radiation alone. Since the snow covering Enceladus would have a near vacuum between the grains, it should be an excellent insulator, almost like a thermos bottle.<blockquote>In reply to:<hr />To support a possible clathrate mechanism is the announcement in one of the Science abstracts of a "mystery" compound whose charge to mass gives a weight of 28 daltons. Several of these can fit into a clathrate cage to be vented with force upon explosive decompresion.<hr /></blockquote>OK, what molecules could have a molecular weight of 28 daltons? The possibilities are few. Wikipedia describes it as molecular nitrogen. Other possibilities are carbon monoxide, ethylene, and hydrogen cyanide with one of the atoms being either carbon 13 or nitrogen 15, both rare isotopes. Carbon 14 doesn't work with hydrogen cyanide, but it would work with acetylene. Somehow I can't see a whole lot of radioactivity going on here, even if there were an extremely strong source of neutrons such as a nuclear reactor. Natural nuclear reactors did indeed happen

silylene old · Mar 14, 2006

reikle - thanks for the excellent links. I have been away the last 4 days, and just got to read them now. Al-26 has a halflife of 726,000 yrs, and thus seems to be an unlikely source of radiogenic heating, in my opinion. It is an extremely rare natural isoptope. The diaper ideas are interesting too. Again the big question is why the diaper still exists today, 4B years after Enceladus formed. While diapers will cause non-spherically symmetric mass distributions, and hence the tidal heating mentioned in the article you linked, I do think after 4B years of axis re-orientation and equilibriation of the ices and sub-surface waters that the moon would become spherically symmetrical - causing the tidal heating engine to slowly grind to a halt. I think if a diaper is the mechanism for heating, then this anomaly would have to have formed relatively recently (begging the question of "how?"). +++ lopsided or off-center core hypothesis: I think a lopsided core could have been produced by a prior collision with a large asteroid. In my concept, the collision would have heated the entire icy surface of Enceldaus up, causing extensive global resurfacing, resulting in the surface we see nowdays. The original crater from this strike I think was lost to view after the extensive resurfacing. However, the fossil remnant of this collision is a lop-sided or off-center rocky core, formed by the merger of Enceladus' original core with the mass of the asteroid. <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>

exoscientist · Mar 14, 2006

Silylene, Al-26 is not the only radioactive isotope proposed to exist in comets early in the solar systems history. There are many. The collected heat of them was proposed to heat the interior of comets. Radioactive isotopes were *detected* in carbonaceous meteorites. From this it as deduced there was enough when the solar system was young to melt water contained in the parent body interiors. Bob Clark <div class="Discussion_UserSignature"> </div>

silylene old · Mar 14, 2006

A diapir would be the conveyor of heat, not the source or mechanism that makes the heat. Hot ice rises. yes and no You are right of course a diapir is a conveyor of heat and is not a source of heat. And hot ice does rise. But a diapir can be a mechanism (for a while) that can cause heat to be produced. If the diapir does exist, it will cause a non-spherically symmetric mas distribution within Enceladus. This will increase tidal heating perhaps significantly within the moon as the moon's axis shift accordingly to compensate under the gravitational tugs of Saturn, the other moons and the sun. The size of a diapir compared to the radius of Enceladus I think might be significant enough to cause enough asymmetric mass distribution to exaggerate a tidal heating mechanism. I think that this tidal heating mechanism will shut down as the mass distribution within the ices in the moon re-equilibrate (and this will happen), which is why I think this is a temporary and not a permanent tidal heating mechanism. <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 · Mar 15, 2006

Good old Wikipedia. It has the following message for the Enceladus article: "This article documents a current event. Information may change rapidly as the event progresses." I read the information that Enceladus' core may have been heated to 1000 degrees K in the discussion forum of Wikipedia and that information has made it into the article now. They attribute this heating to aluminum-26 with a half-life or about 720,000 years (see silylene's post for a more accurate half life, I can't get to that window) and iron 60 with a half life of 1.5 million years. So, after several million years, the core of Enceladus would cool down. 1000 degrees K. would be enough to soften the core and cause it to form a sphere. It should differentiate at that time, with the iron separating out and sinking to the bottom, releasing gravitational energy; that might be enough, with the radiogenic heating, to melt the core. But soon, within just a few million years, the core would refreeze. Any diapirs would face increasing viscosity resistance as the core cools off. Lagrangians at the Saturn/Enceladus L4 and L5 points should be stable there for tens of millions of years. But eventually they will be perturbed out (remember, with objects at both Lagrange points, it is the four body problem, not the three body problem, and it is not stable especially against perturbations from Mimas, Tethys, Dionne, and Rhea, and collisions with small bodies. And also the Sun.) With the Lagrangians being at very close to the same altitude above Saturn as Enceladus, they would collide with Enceladus at that moon's escape velocity, plus a little from the energy that perturbed them out of the Lagrange points. Wikipedia lists the escape velocity of Enceladus in the present era as being 241 meters per second, rather slow. However, Encela

silylene old · Mar 15, 2006

Interesting idea. I have always been fascinated with the concept of slow motion collisions. <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>

bonzelite · Mar 19, 2006

about acetylene (C2H2) excerpt: http://encyclopedia.jrank.org/CAU_CHA/CH4.html Since the heat of combustion of a hydrocarbon is equal to the heat of combustion of the carbon and hydrogen it contains minus its heat of formation, those hydrocarbons with positive heat of formation generate less heat on burning than the elements from which they were formed, whilst those with a negative heat of formation generate more. Thus the heat generated by the combustion of acetylene, C2H2, is 316000 cal., whereas the heat of combustion of the carbon and hydrogen composing it is only 256900 cal., the difference being equal to the negative heat of formation of the acetylene. For substances consisting of carbon, hydrogen and oxygen, a rule was early devised for the purpose of roughly calculating their heat of combustion (J. J. Welter's rule). ---------- excerpt: keck observatory "The two organic compounds found -- acetylene and hydrogen cyanide -- are commonly found in our own solar system, such as the atmospheres of the giant gas planets, the icy surfaces of comets, and the atmosphere of Saturn’s largest moon, Titan. Another carbon-containing species detected, carbon dioxide, is widespread in the atmospheres of Venus, the Earth, and Mars. "If you add hydrogen cyanide, acetylene and water together in a test tube, and give them an appropriate surface on which to be concentrated and react, you'll get a slew of organic compounds including amino acids and a DNA purine base called adenine," said Keck Astronomer Dr. Geoffrey Blake, of the California Institute of Technology in Pasadena and co-author of the paper. “Now, we can detect these same molecules in the planet zone of a star hundreds of light-years away..."

mikeemmert · Mar 20, 2006

<blockquote>In reply to:<hr />One of the attendee's, one Bill McKinnon, said that "the answer for Enceladus is tidal heating, period." - which is the first time I've seen anyone make such a claim, especially as the amount of energy available is supposed to be insufficient to generate the amount of heat we see.<hr /></blockquote>What, my claim and silylene's don't count? OK, I'll second it... Here's a puzzling question: where's the salt? Any ideas?

mikeemmert · Mar 24, 2006

reikel:<blockquote>In reply to:<hr />." Unfortunately, the necessary calculus has so many variables involved that estimating the energy potentially generated under various scenarios is well beyond the boundaries of my mathematical abilities - which probably isn't saying much!<hr /></blockquote> borman:<blockquote>In reply to:<hr />This idea is only qualitative. Even if it were feasible there is no assurance that it could account for the total gigawatt output presently monitored on Enceladus.<hr /></blockquote>If there's anybody capable out there, this idea needs to be investigated. Magnetos certainly work, your weedeater uses one. I would suggest that anybody into such devices make an extremely simple model to see if this is feasible at all or whatsoever. You have an open mind here, go for it. No salt has been detected in the geysers, that's mystifying. That doesn't neccessarily mean there isn't salt deeper in the moon. Salts are common substances. For the induction idea to work, I think you need a conductor. Maybe electroysis converted the salt into perchlorates, which are not very soluble (that's why rocket fuel uses it instead of nitrate, it is more resistant to humidity). In that case, the salt would be gone in just a few years. Something like that might shut down any induction process. Of course, there may be more than one heat source. I think the Lagrangian bumps/tidal heating idea is pretty feasible, of course I'm biased. But so far, that seems to be the best idea yet.

mikeemmert · Mar 24, 2006

Thanks for clarifying about the metal core. Guess I had too much salt on the brain...serves me right for replying to a vogon... I seem to remember that currents are a surface phenomenon, mostly, on metals. The field can't penetrate too deep. That certainly doesn't kill the idea though. I felt great pain when I heard what happened to TSS 1R. That meant it would be harder to make rotovators, one of my favorite ideas. I thought maybe making the tether in sections to isolate currents might be a good idea in this case. Similarly here, it seems like a conductor would have to be continuous and long to generate inductive heating. Grains certainly will not do, they're not connected. As far as physical movement in response to magnetic fields, well, I don't know about that. Maybe. Maybe xillions of particles doing the same thing? Modelers might start by assuming a fully differentiated iron core and seeing if that works, then a salty ocean and seeing if that works, and so on. At this point, we need ballpark figures.

mikeemmert · Mar 24, 2006

<blockquote>In reply to:<hr />Enceladus is somewhat deep in Saturn’s gravity well so arriving impactors can pick up some more kinetic energy before collision. I feel these impacts would rather overpower the signatures of the gentle L4 impacts.<hr /></blockquote>Quite correct about the high speed of any impactors coming from outside of the Saturn system. On the other hand, Lagrangians tend to be huge compared to normal comets/asteroids. Impactors screaming in from the solar system would vaporize completely and tend to plate all the moons with a thin coating of ice. It's quite true these things would cause impactor erosion. They would be falling not only in relation to Saturn, but also the Sun. They carry the energy of dozens or hundreds of times their weight in high explosives. I have done actual extensive modeling of the capture of Triton by Neptune, and I believe Triton formed at one of the two places in the Solar system with the lowest energy with respect to Neptune, and that's the Sun/Neptune L4 and L5 points. The relative energy problem there, bad as it is, is not as bad as 5 - 2/3 times bigger Saturn. If there is radiogenic heating on Enceladus it would almost have to come from a different solar system, one with fresh radioactive elements, and these would hit Enceladus even harder. Let me separate Enceladus and Iapetus and all these moons. I had a personal problem with that for a while and I think it's creating confusion here. Bear with me. Gentle Lagrangian collisions would leave the overall composition pretty much the same for these small bodies. Now, (switching to Tethys) forget Tedesto and Callysto, the present-day Lagrangians of Tethys. Those formed from ice spewed from Enceladus or maybe the source of the black stuff on Iapetus, wha

robnissen · Apr 4, 2006

Thx. for the heads-up.

abq_farside · Apr 5, 2006

It seems to be about Titan, but I would not be surprised if Enceladus gets mentioned as well. It got a very small mention at the end of the program. <div class="Discussion_UserSignature"> Don't let who you are keep you from becoming who you want to be! </div>

telfrow · Apr 10, 2006

Saturn's moon 'best bet for life' Saturn's tiny moon Enceladus may be the best place to look for life elsewhere in the Solar System. That is the view of a senior scientist working on the Cassini spacecraft, which has been studying Saturn and its moons for nearly two years. Dr Bob Brown told a major conference in Vienna, Austria, Enceladus contains simple organic molecules, water and heat, the ingredients for life. ----- "We very clearly saw water; there's water everywhere on Enceladus, it's 99.9% water ice in general at the surface, and we've known that for years, so it wasn't a big surprise," he told the BBC News website. "But when we started looking at our spectra we saw absorption bands from a compound that had to have carbon and hydrogen bonded together. "And when we mapped the location, it was right in these 'tiger stripes' - right where the jets are coming out, and right where it's hot - and it's pretty hard to imagine it's getting there from anywhere but inside." ------ "So Enceladus in a very real sense becomes a stronger candidate for life than [Jupiter's moon] Europa, for instance." Link <div class="Discussion_UserSignature"> Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild. - Tennyson </div>

mikeemmert · Apr 10, 2006

I would like to point out that a sample return mission from Enceladus would be very easy to accomplish. Liftoff is easy in the low gravitational field. Gravitational boosts are available from several moons, including giant Titan, as well as from Jupiter and it's moons. Unlike Mars, targets for sample return are unambigously marked in blue and towering geysers; just drive right up and start collecting. While we're there, a revisit to Titan is also called for. That place has a lot of acetylene and related compounds. A lot has been said about low temperatures on Titan slowing down chemical reactions, but "acetylene can explode with extreme violence (as a) solid." It's freezing point is -84 degrees C. It's shipped disolved in acetone, the wikipedia article on acetone lists that as an important use. I haven't given up on Titan. It is just as important to study biochemistry not as we know it as it is to study life as we know it. Enceladus might have either kind.

chew_on_this · Apr 11, 2006

Minus 180-200 C. is a virtual cryonic ice box. /* deleted */ There is almost certainly nearly a global ocean under the ice. Promoting this life fantasy What fantasy? These are scientists speculating a better than good chance life could prosper in said ocean and there are hints it's is. Believing that there's life on ANY Jovian moon is simply bad science and wild speculation This is REAL science with REAL scientists speculating, not some voodoo headshrinks. The only one doing any believing is you. What a hoot!

chew_on_this · Apr 11, 2006

/*deleted*/ If credibility is a factor, yours is zero, so your statement means zip. Here's the story from one of your favourite sites, so i don't want to hear any &%$#@!in'. Get with the program! http://www.badastronomy.com/bablog/2006/03/09/a-huge-nasa-announcement-today/

paulanderson · Apr 11, 2006

Yet again, you are talking about surface temperatures. The Cassini team has already talked about, in some detail now, how they are pretty much convinced there is liquid water just under the surface and that Enceladus has a molten core, estimated to be up to about 1,400K according to the recent BBC article. This is all based on detailed measurements made by Cassini, not just baseless conjecture. You are entitled to your own beliefs about all this of course, but they are not in agreement with the Cassini team's findings...

mikeemmert · Apr 11, 2006

I think the geysers on Enceladus are excellent and highly credible evidence of a global ocean. There is a source of heat, probably tidal, and just about any model would have the interior warmer than the surface. What we see with regard to the geysers I believe is indicative of what lies beneath the surface. The evidence of a global ocean is also very good at Europa. According to our best understanding of planetary magnetism, a fluid is required. Europa has a magnetic field. The best explanation is moving salty water. As far as your earlier comments about low-temperature chemistry; you note (correctly) that chemical reactions are slower at low temperatures. However, that depends on the exact chemicals you are talking about. For instance, if you mix flourine and hydrogen, they will ignite spontaneously even at a temperature where hydorgen is a liquid and flourine is a solid. And as I have mentioned (with a source, wikipedia, plus there are other sources) frozen acetylene can explode violently. There is not likely free flourine anywhere, but there is plenty of acetylene on Titan. This unstable substance exists on that world because of the low temperatures. Other unstable substances such as ethylene have been found. At warmer temperatures such as found on Earth, such unstable compounds are ephemeral, exisiting only within cells for a fleeting moment as they do their jobs. Any biochemistry which evolves on Europa, Enceladus, or Titan would have completely different chemical pathways suitable for the conditions found there. All three bodies have substances found which are liquid at the temperatures there as best we can determine them. Titan has observed compounds which are reactive at those temperatures, and there's no doubt in my mind that reactive substances will be found at Enceladus.<blockquote>In reply to:<hr />end of story.<hr /></blockquote>Aw, c'mon, Steve. There are things to ex

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