Enceladus, the Europa of Saturn

3488 · Mar 8, 2007

AFAIK, crystalline ice only forms if if freezes slowly or ice that is subjected to warmth, i.e warmer than its surroundings. Crystalline ice is obviously present on Enceladus & has been found on the Pluto moon Charon, Uranus moons Ariel & Titania. It is now suspected on Dione. 2003 EL61 clearly has been 'warmed', together with its weird Rugby ball shape & fast rotation, means that it has been subjected to an enormous impact, probably not that long ago on the Geological timetable. Also remeber that 2003 EL61 has two large moons!!! Andrew Brown. <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>

MeteorWayne · Mar 8, 2007

Thanx, that was my next question <img src="/images/icons/smile.gif" /> <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>

rhm3 · Mar 8, 2007

3488, thank you for those updates. Just curious do you have a link regarding the extended Cassini mission flybys? A close flyby of both Dione and Iapetus would be great and (to me) a nice surprise. I'm also very intrigued that Dione might have activity.

brellis · Mar 9, 2007

hi RHM3 Here's the SDC Cassini thread. www.unmannedspaceflight.com has great stuff too. <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

rhm3 · Mar 11, 2007

Thanks for those links, yeah I do lurk at unmanned spaceflight as well...however I still didn't see anywhere where an extended mission closeup Iapetus encounter is planned (last I heard it was being excluded)...so I'd like to see confirmation of that. The Dione flyby will be interesting, it does seem like it's venting a little bit. To what degree does an object have to vent to be considered "volcanically active"? Io, Enceladus, and Triton are the only other bodies we can say that is the case for sure...if Dione's is so minimal it'd be weird including it in that list.

brellis · Mar 11, 2007

I poked around my usual haunts for mention of Iapetus. Here's a Planetary Society Weblog from my favorite space/science writer, Emily Lakdawalla. We'd love to go back to Iapetus, which has only one close flyby in the prime mission, but it's so far from Saturn that we realized some time ago that we might have to give up on that dream -- getting back to Iapetus might close out too many other options. I'd like to see the next generation Cassini have many little probes available. Why not drop a little manmade trojan behind each moon? I wonder how small a probe can be and still have an effective observing life. <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

rhm3 · Mar 11, 2007

Yeah that was my concern as well. There's a really close flyby this September...perhaps they will give it more consideration if that flyby doesn't help with the mysteries (or finds more)? Alternatively it'll figure out all of the mysteries so we won't need to make another approach...but we know that never happens lol. Someone on that spaceflight board suggested Cassini end its whole mission by landing on Iapetus...I have no idea how feasible that would be but if it does land on a satellite that'd be the best one (Enceladus and Titan are out of question because of contamination issues). Really cool idea and I'm not sure if anyone on the Cassini team has considered it. I'm certainly not diminishing Enceladus and Titan, in fact I'm very much looking forward to the multiple flybys ahead...just wish we didn't have to sacrifice so much to get another Iapetus flyby.

3488 · Mar 12, 2007

A soft landing on Iapetus would not be possible. Cassini would be destroyed on impact (surface gravity of Iapetus is about 2% or one fiftieth of Earth), not to mention that in order to acheive a soft landing Cassini would have to use a lot of fuel, many Titan & Iapetus encounters for orbital trimming, etc. Andrew Brown. <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>

brellis · Mar 12, 2007

Article on NASA's Cassini Page - Scientists are having some success with a 'Hot Start' model that helps explain the chemical signatures observed in the plume. The hot start model suggests Enceladus began as a mixed-up ball of ice and rock that contained rapidly decaying radioactive isotopes of aluminum and iron. The decomposition of those isotopes - over a period of about 7 million years - would produce enormous amounts of heat. This would result in the consolidation of rocky material at the core surrounded by a shell of ice. According to the theory, the remaining, more slowly decaying radioactivity in the core could continue to warm and melt the moon's interior for billions of years, along with tidal forces from Saturn's gravitational tug. Scientists have also found the model helpful in explaining how Enceladus might have produced the chemicals in the plume, as measured by Cassini's ion and neutral mass spectrometer. Matson is lead author of a new study of the plume's composition, which appears in the April issue of the journal Icarus. Although the plume is predominantly made up of water vapor, the spectrometer also detected within the plume minor amounts of gaseous nitrogen, methane, carbon dioxide, propane and acetylene. Scientists were particularly surprised by the nitrogen because they don't think it could have been part of Enceladus' original makeup. Instead, Matson's team suggests it is the product of the decomposition of ammonia deep within the moon, where the warm core and surrounding liquid water meet. The thermal decomposition of ammonia would require temperatures as high as 577 degrees Celsius (1070 degrees Fahrenheit), depending on whether catalysts such as clay minerals are present. And while the long-term decay of radioactive species and current tidal forces alone cannot account for such high tempe <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

exoscientist · Mar 13, 2007

Thanks for that link, Brellis. The scientists noted this early radiogenic heating on Enceladus raises the possibility of life on that moon. Notice that a similar theory had already been proposed to explain aqueous minerals seen in meteorites believed to stem from comets: exoscientist 01/14/06 04:52 PM Re: Enceladus, the Europa of Saturn [re: telfrow] http://uplink.space.com/showthreaded.php?Cat=&Board=sciastro&Number=426379 exoscientist 08/09/06 10:17 AM "The elephant in the room." http://uplink.space.com/showthreaded.php?Cat=&Board=sciastro&Number=550963 Bob Clark <div class="Discussion_UserSignature"> </div>

MeteorWayne · Mar 15, 2007

That's an excellent question, regarding why one pole and not the other? Perhaps it has to do with subtleties of insolation and dynamic distribution of matter under the surface, which might determine local heat. It's a fascinating subject as we get more data to speculate with <img src="/images/icons/smile.gif" /> <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>

silylene old · Mar 16, 2007

Perhaps it has to do with subtleties of insolation and dynamic distribution of matter under the surface, which might determine local heat. Sorry, I don't completely buy into the radioactive heating explanation. To me, it seems unlikely that this one moon would be so unique in this manner (of all the moons orbiting the gas planets). I still think that the cause of the warming is an off-center core, as I proposed long ago. Non-spherically symmetrical mass distribution would exaggerate tidal heating quite a lot. <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>

3488 · Mar 16, 2007

I too do not buy into the Radioactive Isotope explanation. Enceladus is such a small object, where would these materials come from? Why would Enceladus have a substantial quantity? The density of Enceladus is too low to account for the amount of radioactive materials required, after some 4.6 billion years of heating through radioactive decay. I think silylene's explantion is far more likely. A lop sided core would amplify tidal heating. If this is so, than why is it displaced towerds the south pole of Enceladus? Surely it would be displaced towards the centre of the Saturn facing side, would it not??? Mind you, it appears as if Enceladus has rolled over more recently, so perhaps it did until then!!! As MeteorWayne correctly says, this must be researched further. Andrew Brown. <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>

3488 · Mar 19, 2007

I think that the ice plumes will be studied in more detail before then. The 23 km distance is indeed exciting. I hope that high resolution images can be obtained of the vents, along with good spectral readings of the exact composition of the venting materials!! This reminds me of the Galileo orbiter being sent through the plume of the Thor volcano on the Jupiter moon Io. Galileo came through unscathed. I think Cassini will too. Andrew Brown. <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>

silylene old · Mar 19, 2007

Close swing by's will also let us map the internal mass distribution of this moon, to see if there is an off-center core. <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>

brellis · Apr 18, 2007

From the CICLOPS Page On April 24, Cassini reaches its closest point to Saturn during this orbit – called periapse – at a distance of 344,000 km (214,000 mi). During this period, Cassini will observe Saturn’s illuminated ring system as well as two of Saturn’s large inner moons: Dione and Enceladus. Cassini will observe Enceladus on April 24. During this observation, Enceladus will be visible only as a crescent, like the image at right (PIA07758). While this geometry is not suitable for observing the surface, it is perfect for observing Enceladus’ south polar jets that erupt from vents along the moon’s south polar “tiger stripes.” This plume has been observed on multiple occasions over the past 2 years. However this will be the best opportunity to observe the individual jets that form the larger plume since the image at right was taken in late November 2005. Observations such as these will be helpful in understanding the nature of the south polar plume and how the jets erupt. For example, one theory that has been proposed is that the individual jets, which erupt from the prominent fractures crossing the south polar region, are tidally controlled: i.e., they erupt from cracks that open and close due to variations of Saturn’s gravitational pull on Enceladus as it orbits Saturn in its eccentric orbit. Determining the locations of the jets observed during this observation and comparing those to the source vents identified from the previous Cassini images of the jets would help prove or disprove this theory./safety_wrapper> <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

3488 · Apr 19, 2007

From the CICLOPS website. On April 24, Cassini reaches its closest point to Saturn during this orbit – called periapse – at a distance of 344,000 km (214,000 mi). During this period, Cassini will observe Saturn’s illuminated ring system as well as two of Saturn’s large inner moons: Dione and Enceladus. Cassini will observe Enceladus on April 24. During this observation, Enceladus will be visible only as a crescent, like the image at right PIA07758 . While this geometry is not suitable for observing the surface, it is perfect for observing Enceladus’ south polar jets that erupt from vents along the moon’s south polar “tiger stripes.” This plume has been observed on multiple occasions over the past 2 years. However this will be the best opportunity to observe the individual jets that form the larger plume since the image at right was taken in late November 2005. Observations such as these will be helpful in understanding the nature of the south polar plume and how the jets erupt. For example, one theory that has been proposed is that the individual jets, which erupt from the prominent fractures crossing the south polar region, are tidally controlled: i.e., they erupt from cracks that open and close due to variations of Saturn’s gravitational pull on Enceladus as it orbits Saturn in its eccentric orbit. Determining the locations of the jets observed during this observation and comparing those to the source vents identified from the previous Cassini images of the jets would help prove or disprove this theory. CICLOPS/JPL. ============================================================================== Hopefully these observations will nail down once & for all, the heating mechanism of the south polar region of Enceladus. I see your point borman. If the 'throat' as you call it is not cleared, that vent will shut down & freeze up. With <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>

3488 · Apr 25, 2007

New observations of the Enceladus south polar plumes!!! N00081671.jpg was taken on April 24, 2007 and received on Earth April 25, 2007. The camera was pointing toward ENCELADUS at approximately 190,884 kilometers away, and the image was taken using the CL1 and CL2 filters. Andrew Brown. <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>

3488 · Apr 25, 2007

N00081664.jpg was taken on April 24, 2007 and received on Earth April 25, 2007. The camera was pointing toward ENCELADUS at approximately 189,299 kilometers away, and the image was taken using the CL1 and CL2 filters. Andrew Brown. <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>

3488 · Apr 25, 2007

A nice high phase shot of the south polar region of Enceladus. N00081661.jpg was taken on April 24, 2007 and received on Earth April 25, 2007. The camera was pointing toward ENCELADUS at approximately 183,033 kilometers away, and the image was taken using the P0 and CL2 filters. Andrew Brown. <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>

3488 · May 17, 2007

Frictional heating explains plumes on Saturn moon NASA NEWS RELEASE Posted: May 16, 2007 GREENBELT, Md. - Cracks in the icy surface of Saturn's moon Enceladus open and close daily under the pull of Saturn's gravity, according to new calculations by NASA-sponsored researchers. "Tides generated by Saturn's gravity could control the timing of eruptions from cracks in the southern hemisphere of Enceladus," said Dr. Terry Hurford of NASA's Goddard Space Flight Center, Greenbelt, Md. Hurford is lead author of a paper on this research appearing in Nature May 17. This paper is one of two studies on Enceladus in this issue of Nature. The other paper explains that tidal forces cause the sides of the cracks to rub together and produce enough heat to vaporize ice into plumes that jettison off the moon, researchers suggest. Plumes of water vapor and other gases escape at high velocity from the surface of Saturn's moon Enceladus, as shown in this artist concept. Credit: NASA/JPL In 2005, the Cassini spacecraft flew by Enceladus and saw plumes of material erupting from the south pole of Enceladus. Scientists were surprised to see this because eruptions are powered by heat from an object's interior. Enceladus is tiny compared to most moons, only about 500 kilometers (310 miles) in diameter, so it should have lost its interior heat to the cold of space long ago. A closer look by Cassini revealed a series of 120-kilometer (75-mile) long cracks in the south polar region of Enceladus, which were nicknamed "Tiger Stripes" because they resembled a tiger's distinctive marks. The stripes are warmer than their surroundings, so scientists believe they are the source of the eruptions. The Cassini observations also show the plumes consist of water vapor, so there is evidence for liquid water under the ice. Since liquid water is necessary to support known forms of life, Enceladus has become a promising place to look for extraterrestrial <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>

brellis · May 17, 2007

hi borman Note that Enceladus is rather singular in this energy signature and that other moons suffering even greater tidal force do not exhibit geysers. {If I'm following the thinking correctly...} We're calling the Enceladus outgassing a geyser because needs to be heated from within by some kind of process. A faint outgassing has been spotted emanating from Dione, but confirmation requires UV sampling, which Cassini will do on a future pass. Chances are better the Dione outgassing is secondhand ice rather than a little geyser. Dione likely has some cryovolcanoes smoothing its surface. Note that there are fractures on Europa as well that can also be maintained by Juptier's tidal forces. Even though the secondary magnetic field suggests a liquid salty ocean at some depth upon Europa, there has been no observation of any plumes there as yet even though the fractures are tidally maintained. Using information gleaned from Enceladus has helped sharpen our ability to spot outgassing, as proven by the Dione announcement. Question: did Galileo or New Horizons take any UV measurements of Europa that might increase our understanding of the surface environment? A-Googling I will go, A-Googling I will go... *whistling* From JPL's Galileo Page Ruddy Freckles on Europa Reddish spots on the icy surface of Jupiter's moon Europa may indicate pockets of warmer ice rising from below. This upwelling could provide an elevator ride t <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

brellis · May 17, 2007

Yes, geysers would have been a big deal, but since Europa does have some kind of tenuous atmosphere, could there in fact be some indications of the processes to be gleaned from earlier observations. Might there be a reason to reexamine existing data from Europa based on the discoveries at Saturn? I beieve the reddish spots on Europa are now more thought to be due to sulfur contamination from Io. Maybe we can ask Anthmartian to sew together a set of visuals illustrating the advancements of our understanding of the surface of Europa, and put it on our DVD <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

silylene old · May 17, 2007

I have reservations about whether the total heat budget can be accounted for by this tidal mechanism. It could be accounted for if the mass distribution of Encelaudus is non-spherically symmetric. For example, if the core of the moon were off-center, this would greatly amplify the tidal heating. I proposed this asymmetry concept shortly after I proposed that the tiger stipes were warm enough to form liquid water (scroll back through the original Enceldaus thread, you will find it). This liquid water warmth guess was subsequently confirmed when the geysers were discovered. I was not surprised, I had confidently predicted it many months earlier. I also predict that 1) theoretical modeling studies will support that an off-center core will amplify tidal heating. In fact, more recently some models with off-center sub-surface water reservoirs are hinting at this. And 2) that after several close passes to the moon, the gravitational field will be well enough mapped to find that the mass distribution is curiously non-spherically symmteric. We shall see. I am very patient. <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>

h2ouniverse · May 18, 2007

Hi Borman, I could attend recently at EGU a presentation by G. Tobie (LPG Nantes), very convincing to me, comparing models with three assumptions for Enceladus (from surface to core): 1) hard ice shelf / warm soft ice / rocky core 2) hard ice shelf / global ocean / rocky core 3) hard ice shelf / local sea at South pole (and hard ice elsewhere) / rocky core The study concludes to assumption 3 (South polar sea, with contact between rocky core and water). Best regards. (*) EGU2007-A-04974; PS3.1-1TH5O-002 Tobie, G.; Cadek, O.; Sotin, C. Tidal heating, liquid water and the origin of the South Polar Hot Spot on Enceladus

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