Enceladus, the Europa of Saturn

[robnissen]

You said: "Assuming that the interior of the planet is going to be warmer than the surface is an interesting hypothesis. . .<br /><br />However, it's observation which will establish that. And unlike some, I don't have to retreat into ignorance about the interior temps, or into places which have not and cannot be observed on this mission, in order to support a position."<br /><br />But the fact that the interior is warmer than than the surface is more than an interesting hypothesis because "observation" has established that there is a significant heat difference betweens the cracks and the surrounding surface area. There is NO hypothesis that that heat difference is related to ANY surface activity, so the only possible place for the heat difference to come from is the interior. Now whether the heat difference is sufficient to support a liquid water/ammonia mix, that is currently unknown. But "observation" has demonstrated that there is some sort of a heat source in the interior.<br /><br />BTW, NASA's own web site states "Scientists find the temperatures difficult to explain if sunlight is the only heat source. More likely, a portion of the polar region, including the "tiger stripe" fractures, is warmed by heat escaping from the interior."<br /><br />

 

[robnissen]

Apparently there is only one more close flyby planned for Enceladus: <br />"Cassini has years of work ahead; the next and final close encounter with Enceladus does not take place until 2008."<br /><br />Does anyone know if due to the recent stunning developments, that there would be any possibility of changing the orbit so that there would be more than one future close flyby?

 

[chew_on_this]

I think Rob said it well enough. Observation IS what brings us to the conclusion of interior heating. Nuff said.

 

[silylene old]

<font color="yellow">"The temperatures could be as high as 110 K, 30 kelvin warmer than the area outside the fissures." <br /><br />Let's see, 110 K is Minus 153 C. Hmmm. Still cryonic, still not liquid water. Not a sign of oceans. And the rest of the place is Minus 183 C., the same temps basically as the Titan surface, among others. Methane freezes at that temp. <br /></font><br /><br />As I understand it, the temperature from the IR measurement is the <i>average</i> temperature measured over the entire measurement area. The 110K may not be the exact temperature of the fissure; actually it's just one knowledgable person's estimate. All we do know is that the average of the area of the hot fissure and the area of the surrounding cold ice surface was found to be 91K.<br /><br />So I will make an estimate too....<br />If the 5% of the area in the box is occupied by a fissure at a balmy 300K, and the 95% of the area of the box surrounding surface is a frigid 80K, then the average temperature seen by the detector = 0.05*300 + 0.95*80 = 91K.<br /><br />In my estimate, I assumed 5% of the fissure was actually open and shedding heat (this assumption made my numbers look good! Actually I wanted to illustrate that there might actually be some significant heat source if it is small and localized in the center of a cracked ice surface.)<br /><br /><i>edit: ciclops is up. Looked at the original data and changed a few assumptions. Picture posted after this.</i> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[silylene old]

Actual thermal data from ciclops:<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Does anyone know if due to the recent stunning developments, that there would be any possibility of changing the orbit so that there would be more than one future close flyby?<p><hr /></p></p></blockquote><br /><br />Pretty much nil until after the primary mission is complete, because such a modification would most likely sacrifice other mission objectives. That won't be a problem after the primary mission, however. (Competition with other interesting targets *will* be a problem, of course.)<br /><br />The 2008 flyby is actually near the end of the primary mission: during the High Inclination Sequence. (The mission has been sorted into sequences of orbits designed to acheive certain observations, mainly of Saturn itself.) The current phase is the Occultation Sequence, designed primarily to allow occultation observations, where Cassini watches for eclipses of the Sun and Earth behind Saturn, the rings, Titan, and various other objects. You can read more about the primary mission's tour at this page. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"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."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[centsworth_II]

Well, when we get some confirmed facts, we'll be sure to tap you on the shoulder so you can take your thumbs out of your ears and your hands from over your eyes.<img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> </div>

 

[chew_on_this]

Didn't I post this for steve already?

 

[chew_on_this]

<font color="yellow">The images are of the surface, not the interior. Cassini has no way of sending down probes which can probe inside the south pole of Enceladus. The beliefs that these moons have warm cores is an hypothesis which has not been tested, nor can it be, easily with what's on Cassini. </font><br /><br />Priceless. So where, pray tell, is the heat coming from oh perveyor of scientific truths?<br /><br /><font color="yellow">So far, such beliefs are simply wishful thinking driven by motivations which are far from scientific. More deviation from good science by exobiophiliotic beliefs, frankly</font><br /><br />Doubly priceless. You sure know how to stick it to us don't ya? The only one being unscientific is you considering you are providing no other solutions to the source of heat.<br /><br />

 

[chew_on_this]

From CICLOPS:<br /><br />August 30, 2005<br /><br /><br /><br />Dear Friends and Colleagues, <br /><br /><br />Today, at a press briefing in London, the Cassini Imaging Team and several other Cassini science teams announced dramatic findings from the recent, July 14 scraping encounter with the small icy moon, Enceladus. All signs point to a very unusual, surprisingly warm and young south polar region, crossed by a set of distinctive fractures that are rich in organic materials and actively venting water vapor and icy powder-sized particles to space. <br /><br /><br />These startling discoveries can explain the source of the diffuse E ring in which Enceladus is embedded in its orbit around Saturn. They also distinguish Enceladus as one of the few presently active bodies in the solar system, despite its diminutive size, and broaden our grasp of the diversity of planetary environments found today in orbit around our Sun. <br /><br /><br />Visit ... <br /><br /><br /> http://ciclops.org<br /><br /><br />... for the latest image products and more information.<br /><br /><br />A detailed press release will be posted to Newsroom on the CICLOPS website later in the day.<br /><br /><br /><br />Enjoy!<br /><br /><br />Carolyn Porco<br />Cassini Imaging Team Leader<br />Director/CICLOPS<br />Space Science Institute<br />Boulder, CO<br />

 

[chew_on_this]

Get a life. Some people value the granduer of the cosmos and some, such as yourself, are just a stick in the mud.

 

[tom_hobbes]

<font color="yellow">Enceladus has nothing in common with Europe</font><br /><br />I think you'll find that French waiters can be equally chilly from time to time. <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>

 

[chew_on_this]

<font color="yellow">I'm very much like Sagan...</font><br /><br />No, you're not. Sagan was right most of the time and people actually cared what he had to say.

 

[telfrow]

<b>Cassini Finds Enceladus Tiger Stripes Are Really Cubs</b><br /><br /><i>The Cassini spacecraft has discovered the long, cracked features dubbed "tiger stripes" on Saturn's icy moon Enceladus are very young -- between 10 and 1,000 years young. <br /><br />These findings support previous results showing the moon's southern pole is active. The pole had episodes of geologic activity as recently as 10 years ago. These cracked features are approximately 130 kilometers long (80 miles), spaced about 40 kilometers (25 miles) apart and run roughly parallel to one another. <br /><br />The cracks act like vents. They spew vapor and fine ice water particles that have become ice crystals. This crystallization process can be dated, which helped scientists pin down the age of the features. <br /><br />"There appears to be a continual supply of fresh, crystalline ice at the tiger stripes, which could have been very recently resurfaced," said Dr. Bonnie Buratti. She is a team member of the Cassini visual and infrared mapping spectrometer at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Enceladus is constantly evolving and getting a makeover." <br /><br />This finding is especially exciting because ground-based observers have seen tiny Enceladus brighten as its south pole was visible from Earth. Cassini allows scientists to see close up that the brightening is caused by geologic activity. When NASA's Voyager 2 spacecraft flew over the moon's north pole in 1981, it did not observe the tiger stripes. <br /><br />Cassini's visual and infrared mapping spectrometer shows water ice exists in two forms on Enceladus: in pristine, crystalline ice and radiation-damaged amorphous ice. <br /><br />When ice comes out of the "hot" cracks, or "tiger stripes," at the south pole, it forms as fresh, crystalline ice. As the ice near the poles remains cold and undisturbed, it ages and converts to amorphous ice. Since this process is believed to take place over decades or less, the tiger stripes must be very y</i> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[telfrow]

<i>This graphic represents a possible model for mechanisms that could generate the water vapor and tiny ice particles detected by Cassini over the southern polar terrain on Enceladus. This model shows venting by "plumes." <br /><br />For other models being considered by scientists, see also </i><br /><br />http://www.nasa.gov/mission_pages/cassini/multimedia/pia07725.html <br /><br /><i>and</i> <br /><br />http://www.nasa.gov/mission_pages/cassini/multimedia/pia07727.html. <br /><br /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[telfrow]

<i>This plot shows results from Cassini's ion neutral mass spectrometer and cosmic dust analyzer, obtained during the spacecraft's close approach to Enceladus on July 14, 2005. <br /><br />Within a minute of that closest approach, the two instruments detected material coming from the surface of the moon. The ion neutral mass spectrometer measured a large peak in the abundance of water vapor at approximately 35 seconds before closest approach to Enceladus, as it flew over the south polar region at an altitude of 270 kilometers (168 miles). <br /><br />The high rate detector of the cosmic dust analyzer observed a peak in the number of fine, powder-sized icy particles coming from the surface approximately a minute before reaching closest approach, at an altitude of 460 kilometers (286 miles). <br /><br />The character of these detections is very similar to the venting of vapor and fine, icy particles from the surfaces of comets when they are warmed as they near the Sun. On Enceladus however, it is believed that internal heat, possibly from tidal forces, is responsible for the activity. The close but different occurrences of the two detections are yielding important clues to the location of the vents and even the venting process. </i><br /><br />http://www.nasa.gov/mission_pages/cassini/multimedia/pia03553.html <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[telfrow]

<b>Enceladus Atmosphere Not Global</b><br /><br /><i>On July 11, 2005, the Cassini ultraviolet imaging spectrograph observed the star Bellatrix as it passed behind Enceladus, as seen from the spacecraft. The starlight was observed to dim when it got close to Enceladus, indicating the presence of an atmosphere, as illustrated in figure A. The ultraviolet imaging spectrograph team was able to identify water vapor as the composition of the atmosphere from absorption features in the spectrum of the star. From the depth of the absorption features, it was also possible to estimate the quantity of water vapor the starlight passed through. The colors show the undimmed star signal (blue) versus the dimmed star signal (pinkish). <br /><br />Enceladus' atmosphere is localized, not global in extent. As Bellatrix re-emerged from behind Enceladus, there was no dimming of the starlight observed. An occultation of the star Lambda Scorpius in February also showed no sign of an atmosphere, as illustrated in figure B. In figure A and B, the arrow marks the path of the star as it was blocked from view by Enceladus. In figure A, the dimming of the starlight shows as a gradual decrease in brightness, while in figure B the starlight drops abruptly just at the point in time that the star goes behind Enceladus. </i><br /><br />http://www.nasa.gov/mission_pages/cassini/multimedia/pia03552.html<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[chew_on_this]

Seems odd the scientists think tidal forces are responsible for the interior heating especially in such a localized region.

 

[telfrow]

I found this, which offers a few ideas on the localized tidal effect:<br /><br /><b>Giant water plume spews from Saturn’s moon</b><br />16:07 30 August 2005 <br />NewScientist.com news service <br />Stephen Battersby <br /><br /><i>Tidal friction<br />Internal heat must be driving all this activity, but the source of the heat remains a big puzzle. Natural radioactive decay in the moon's rocky core might warm the interior just enough to produce a sludgy plume of water and ammonia. This could heat the surface ice just enough to allow water to evaporate slowly. <br /><br />But Cassini also detected dust and whole ice grains in the plume, implying that the material is squirted out of Enceladus with some force. That would need a lot of heat – far too much to come from the core. <br /><br />An alternative is the tidal pull of Saturn's gravity, which makes the moon flex and produce heat by internal friction. But initial calculations put that at only 1% of the heat from the core.<br /><br />Johnson speculates that thousands of years ago the orbit of Enceladus may have been different, producing much more severe tidal heating. Today, researchers just see leftover heat escaping. <br /><br />Or perhaps all the tidal stresses on Enceladus are focused on those four fissures, rubbing the surfaces together to melt the ice. "Somehow Enceladus is doing it, so we're going to have to figure out how," says Johnson.</i><br /><br />That's just the section dealing with tidal effects. The entire article, which deals with other topics, can be found at:<br /><br />http://www.newscientistspace.com/article.ns?id=dn7924<br /><br /><br /> <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[mrmux]

The Metro, a free daily newspaper here in the UK, has solved it folks. Wed Aug 31st:<br /><br />"They have discovered the 500km-wide moon acts like a pressure cooker, shooting jets of ice and water vapour from its south pole..."<br /><br />At least the picture was nice.

 

[telfrow]

Here's the photo of the plume... <div class="Discussion_UserSignature"> <strong><font color="#3366ff">Made weak by time and fate, but strong in will to strive, to seek, to find and not to yeild.</font> - <font color="#3366ff"><em>Tennyson</em></font></strong> </div>

 

[tom_hobbes]

Looks mostly like blurring from the composite nature of the image. <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>

 

[chew_on_this]

Looks like another intriguing moon we'll probably not get any concrete answer to in out lifetime. Shucks, I hope life extension pans out before I go to valhalla.

 

[vogon13]

Just throwing out an idea here, have not thought it through so if its' whacked be nice.<br /><br />How different is the thermal conductivity of a solid block of water ice versus non-compacted grains and snowflakes and crystals of ice deposited in a vacuum?<br /><br />If the Enceladosian surface is covered with a more insulating form of ice than expected, can the internal heating source be proportionally weaker for the same observed effects?<br /><br />I am assuming the weak surface gravity will allow this loose insulating blanket to accumulate to a much greater depth than is observed on earth.<br /><br />Plausible?<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[silylene old]

Dione looks like an "extinct" Enceladus. Perhaps in its early history, it somehow had active faults that spewed water crystal, or whatever. Judging from the crater density, it appears not to have been resurfaced for a very long time, and so it must have been extinct for eons.<br /><br />So I offer a picture of Dione, the "Extinct Enceladus": <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>