New press release by the imaging team:

Cassini Pinpoints Hot Sources of Jets on Enceladus
October 10, 2007
(Source: Space Science Institute)

CICLOPS link to the release here.

One thing I was curious about tiger stripe naming - why didn't they switch "Baghdad" and "Cairo" so we have a nice A,B,C,D progression? I can only imagine it was done on purpose, but why?

Joe Spitale and Carolyn Porco have a paper in Nature, out tomorrow but online today, on the sources of Enceladus' South Polar jets entitled, "Association of the jets of Enceladus with the warmest regions on its south-polar fractures." As you can tell from the title, many of the jet sources are located near hotspots seen by CIRS, and nearly all are located along one of the tiger stripes in the south polar region. For those without access to the article, there is a press release located at http://saturn.jpl.nasa.gov/news/press-rele....cfm?newsID=780 . In addition, a map showing the hotspot and jet source locations can be found at http://photojournal.jpl.nasa.gov/catalog/PIA08385 . These are really intriguing results, and it would be interesting to see how these sources match up with those of the jets seen a couple of weeks ago. Are the sources variable? Are different parts of the stripes active at different times (as Terry Hurford suggests) or are they more constant and tied to thermal emission sites (as Spitale and Porco suggest)?

Enjoy!

All..

I had seen this earlier in the AGU Abtracts but declined to post until we had some fuller reporting.
Unfortunately, this is all that has came forward so far.....


"Sodium issue clouds Enceladus"
http://news.bbc.co.uk/2/hi/science/nature/7145530.stm

quoting from this press release....

"A chemical analysis of Enceladus, led by University of Colorado planetary scientist Nick Schneider, failed to detect sodium, an element scientists say should be in a body of water that has had billions of years of contact with rock.

"If you have a long-lived ocean, it's going to have salt in it," said Dr Schneider, at the American Geophysical Union (AGU) meeting in San Francisco this week, "but that ocean, if it exists on Enceladus, isn't leaking out into space."

"Critics of the study accept his observations, but disagree with his conclusion; and it has led to some robust exchanges here at the AGU meeting this past week. "

March flyby through the plumes is gonna be really interesting....

Craig

Interesting to see this sodium discussion continuing. There was also robust discussion after a similar talk by Nick Schneider at the August Outer Planet Satellites workshop.

Very interesting indeed.

No Saknussemm Sea? (called this in the movie, not the book.... but it sounds better)
http://www.online-literature.com/verne/jou...enter_earth/30/


Cold Faithful - high temperature source for plumes
http://www.planetary.org/news/2007/0322_Ch...est_a_Soup.html
http://www.sciencenews.org/articles/20060506/bob9.asp
The process that converts NH3 to N2 and also creates CH4 through serpentization, involves reaction with a silicate core. Hard to see how the salts would be segregated out of the plumes.

Are the salts all in a non-ionized state and invisible? Can INMS detect salts?

Frigid Faithful - low temperature source for plumes
http://www.planetary.org/news/2006/1214_Ne..._Plumes_on.html
Are the organics at the plume sources captured from other sources in the Saturn system? Or primordial leftovers, not endogenic?

curiouser and curiouser....

Enceladus ain't easy..

Glorious....

Craig

Yet another Enceladus plume model

Dfortes... Clathrate Faithful? (Although Frigid Faithful also depends on clathrates, I believe)

Very interesting, sir.

I have to assume you are the autthor of this paper?

The paper mentions hydrothermal processing ..... as these xenoliths migrate upwards, would they drag "salts" up with them as well?

As much as I want that ocean to be there, the sodium issue makes me pause. What is really going on here, and what is the plume source? And what powers it?


Craig

Interesting indeed. Did the Keck observations search for any other elemental signatures other then Na, or was this even practical?

Thanks, yeah it's mine. I originally (in a moment of wholly uncharacteristic cynicism) called it tepid faithful. Settled on frothy faithful in the end. The difference with the existing clathrate model is that dissociation occurs in warm rising cryomagma whereas the Kieffer model is entirely dry.

As for the sodium - it is not obvious to me that this rules out the presence of an ocean. I would expect any salts to be carried in aqueous solution and be partitioned into hydrated crystalline phase on eruption, so you would not see the expected spectral signature. In the near IR these hydrated salts will appear similar to ice. Whether or not these salts would become coloured after radiation processing I do not know. Sputtering might yield a small flux of cations - depends on the salt; might be Na, Mg, NH4 etc...

Dom

Frothy Faithful... I LIKE that.

Thanks for the clarification between the Frothy and Frigid models, Dom. And your take on the sodium issue. I feel a little more reassured regarding an ocean.

UMSF is greatly enriched by having researchers and mission ops folks among it's members.

Thanks again.

Craig

http://saturn.jpl.nasa.gov/news/features/feature20080207.cfm - Enceladus plume model... scientists suggest an underground lake.

March 12 flyby description available at Ciclops.

Here's a nice powerpoint I came across about Enceladus and its heating - by Tanya Harrison. The pros and cons of the liquid H2O vs clathrate hypotheses are summarized.

http://mgilmore.web.wesleyan.edu/wescourse...1/enceladus.ppt

From http://ciclops.org/index.php
"And most exciting of all: the highest temperatures now measured are about 180 Kelvins, some 63 degrees Fahrenheit warmer than estimated from previous measurements. Though by no means a guarantee, these results make the possibility of liquid water close to the surface of the moon even more likely. Sacre bleu!..."

Water water everywhere !!!!!

Maybe . . . .

no, probably not.

All... the news above from my post last year has bothered me since I first read it. However in slide 15 of this CASSINI team CHARM presentation, looks like CASSINI has found the sodium....
http://saturn.jpl.nasa.gov/multimedia/prod..._Cuzzi_Seal.pdf

"CDA in situ measurements show water, sodium, silicon in E ring grains, and even some metallic grains which may be on unusual orbits"

Can hardly wait for the team's update on data from the August flyby... and we have two more flyby's coming up next month!!! Wonder if they are hanging onto these results until after those encounters?

Very Cool!!!!

Craig

I have a feeling they will wait to release the results, but I hope they don't!

I hope not, too. I wonder how many icy moons in the Solar System will turn out to have subsurface oceans - Europa looks very promising, and now Enceladus...

...and according to some sources, Ganymede and even Callisto may have subsurface oceans, albeit not of the extent of Europa's.

-the other Doug

Not forgetting Titan, where the solid ice crust has actually been observed floating around a bit relative to the interior - possibly the strongest evidence so far of an internal ocean anywhere. Other possibilities include Neptune's Triton and non-moon Pluto.

Speaking of the jets, check out this night side image - http://saturn.jpl.nasa.gov/multimedia/imag...ails168613.html

Here is a shorter exposure to go with it.... http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=168612

Maybe middle-sized moons, too, if they contain ammonia which acts like an antifreeze.
http://blog.wired.com/sterling/2008/09/involuted-ocean.html

Just curious if anyone knows if the R factor of snow increases or decreases if it is in vacuum. If a fluffy surface layer traps heat better than solid ice, and even better if it is vacu-foofed, maybe the internal energy source can be smaller and easier to explain.

Quite the images. Interesting that the plumes are visible without a super high phase angle (i.e. a fairly appreciable crescent noted). Comparison to the Saturnshine gives one a nice sense of the plumes' brightness.

I know I'm being impatient, and I know that the cassini team have a lot of work to do, but, well I was wondering if it would be worth e-mailing the team and asking if they planned to hold onto the most recent flyby data until after the next two Enceladus flybys. It wouldn't surprise me if they did but, well, I'm just wondering whats happened to it?

All..

found the following paper online
"The E-ring in the vicinity of Enceladus II. Probing the moon’s interior—The composition of E-ring particles"

"Abstract
The population of Saturn’s outermost tenuous E-ring is dominated by tiny water ice particles. Active volcanism on the moon Enceladus, embedded in the E-ring, has since late 2005 been known to be a major source of particles replenishing the ring. Therefore particles in the vicinity of Enceladus may provide crucial information about the dynamical and chemical processes occurring below the moon’s icy surface. Here we present a statistical evaluation of more than 2000 impact ionisation mass spectra of Saturn’s E-ring particles, with sizes predominantly below 1 μm, detected by the Cosmic Dust Analyser onboard the Cassini spacecraft. We focus on the identification of non-water features in spectra otherwise dominated by water ice signatures. Here we specify the categorisation of two different spectrum types, which probably represent two particle populations. Type I spectra imply pure water ice particles, whereas in Type II spectra organic compounds and/or silicate minerals are identified as impurities within the icy particles. This finding supports the hypothesis of a dynamic interaction of Enceladus’ rocky core with liquid water."
© 2007 Elsevier Inc. All rights reserved.

http://lasp.colorado.edu/~horanyi/FTP/Cass...-ring2_2007.pdf

This report details data from the 2005 Enceladus encounters.

From this, the sodium detection appears to be contamination from the detector but the silicate detection is firm.

Enjoy..

Craig

They seem to have a good handle on the sodium contamination, would they not take it into account before claiming they had found sodium in the E-ring?

I've decided against badgering the Cassini team (the right and obvious decision but impatience skews my perception sometimes), I'm sure they've got enough on their plates.

Keep in mind that this report is from data acquired in 2005. The team may have gotten better data since then.

All be be revealed in due time, I am sure. These teams are no doubt very busy getting together presentations for the upcoming DPS.

Craig

New article in Nature according to recent space.com article. Looks like there is evidence for a large body of salty water deep in Enceladus, but that the jets are fueled by slow evaporation deep underground.

The evidence for sodium salts is indirect, coming from E ring dust particles rather than Enceladus jets. (Quoi?)

So more like a humidifier in the corner rather than "Cold Faithful".

In the Geophysical Research Abstracts, Postberg et al. claim to have found Na in the plumes.

Sodium Salts in Ice Grains from Enceladus' Plumes

This was picked up by the New Scientist, MSNBC and the BBC. (See my posts in the October 31 thread (I don't seem to be able to insert links correctly))

I would love to see a discussion of this finding is relation to the current news.

The current understanding of the geysers of Enceladus

One says that the presence of Na salts in the E-ring implies an ocean on Enceladus.

Another group says that Enceladus has as much Na (note here they are mentioning the plumes) as there is in a glass of relatvely pure water (metaphorically speaking). So they suggest that the plumes are rather like an air conditioner set to gentle breeze rather than geyser speed

Now a question, how do you connect gigawatts of heat energy incorporated in the plumes with gentle breeze speed?

A clarification- according to the "misty caverns" idea, the water vapor evaporates from the salt-water interface at a slow, gentle rate, but over a large area, and by doing so it builds up pressure in those chambers, and then it rushes out the "leaks" in the narrow fractures beneath the tiger stripes at supersonic speeds, plenty fast enough (we think) to keep the surface warm. The speed of ejection from the surface is similar in the "geyser" model and the "misty cavern" model- the difference is just whether liquid water is involved near the surface.

The slow evaporation from large water surfaces was an idea that originated with the CDA team, in fact, but it helps nicely to reconcile the two data sets.

We put together a graphic as part of the Cassini web release that I hope explains the options in a somewhat comprehensible form. The different interpretations have proved tricky to explain to people, and of course there may be even better models that we haven't thought of yet. So further suggestions are welcome!

John.

John, just for baseline purposes, what's the latest leading model for Enceladus' heat source? Was a single specific type (localized radioactive, global tidal with a south polar soft spot, etc.) postulated to derive these plume models?

It's gotta be tidal heat- radioactive heat isn't nearly enough. The questions involve where the heat is dissipated (in shallow fractures? More broadly throughout the south polar ice shell?) and what's happening with its orbit, and its interaction with Saturn and Dione, to keep the heating going.

John

Is it fair to say, then, that the primary constraint on plume models might be the thickness of the ice shell? Seems like that would be largely a function of the amount of tidal heating.

Re the localized nature of the plumes: Too bad that a decent gravimetric map of Enceladus seems pretty difficult to obtain. Willing to bet that there's some sort of asymmetry in the rocky part to account for this.

Ice shell thickness is important, though the thickness of the cold, brittle, surface layer versus the warm, ductile, regions is maybe the most important thing. That's not just a matter of total heat flow, it's a matter of how the heat is distributed, too.

We'll be getting some gravity data next Spring, and some more in the XXM if that's approved by NASA. So we may have some constraints before too long.

John

This is not scientific, but I love the "misty caverns" model.... imagine spelunking those! Really love how mysterious and complex Enceladus is... so much to learn.

So glad amateurs like myself have unmannedspaceflight to help in these journeys.

Thanks all!!!

Craig

Enceladus Wharrgarbl
Click to view attachment

...Yeah, that poor mutt might get one Wharrgarbl out before he froze solid!


Good news re gravity data, John, thanks! More reason than ever to root for the XXM. I don't see any way to crack this nut short of getting that, and given the tiny size of Enceladus I'm betting that there will be a substantial anomaly in mass distribution...at least one.

Keep hearing 15GW as the heat output, and not sure what that number signifies or how it's derived. Only thing I can think of is that's the energy needed to fire off the observed plumes and therefore doesn't really set a limit on the total amount of global heat production? The ice shell structure would presumably be a function of total heat output since ice/water is such a good heat sink...

Some interesting stuff at the planetary society and some tantalising abstracts.

Interesting report on spaceref.

Ammonia, at last.

Saturnian Moon Shows Evidence of Ammonia

A longer report at Physorg.com http://www.physorg.com/news167498118.html

Also ....."The fact that we found a lot of argon 40 also argues for liquid water," Lunine said. Liquid water most likely circulating through Enceladus' rocky core is the best explanation for all the argon 40 detected, he said.

And there was (reconfirming earlier detection) ....."an abundance of carbon-bearing molecules, or "organics," entrained in the water vapor.......... (such) as methane, formaldehyde, ethanol and hydrocarbons."

What's the limit of detecting/identifying heavier carbon molecules? Very interesting they have got this far in their analysis. Roll on the Nov flybys!!

I listened in on the CHARM teleconference with Postberg today, and he seems to think it is very scientific. PDF Presentation

He made what seems a strong case that the distribution of particles in the E-ring must come from pools of effervescent liquid salt water within a kilometer or two (or less) of the surface of the south pole. Depending on how much convection there is, the pools are likely to have a total area of hundreds to thousands of square kilometers. He has a slide of Terran ice caves and hypothesizes complex arches and pillars in the gravity field that is little more than 1% of that on Earth.

I am sure that there will be further debate, but the image that he suggests is a very "mysterious and complex" environment. I can't wait until the the artists run with this vision.

Thanks for the heads up Ron!!!

Slide 19.... wow...imagine wandering the caverns on Enceladus, spotlight in gloved hand. The light cacscading off the crusty ice arches! That would be a numinous experience!

Craig

I am right there with you, Craig. Actually, I am dreaming of high-tech gondolas carrying tourists among the caverns. Of course, a hydrobot/cryobot would do just fine. If these things do exist, they will be among the most wondrous environments discovered by the scientific imagination.

I wonder if Cassini's radar could try to catch a reflection off the pools?

Geyser-related story up on the BBC Sci Tech web page today: http://news.bbc.co.uk/1/hi/sci/tech/8495663.stm

Another story from space.com: http://www.space.com/scienceastronomy/ence...ter-100209.html

ADMIN EDIT: Exobiology comments deleted per section 1.3 of the Forum Rules. Please take a moment to review them again.

Edit: My apology for not reading the rules the first time, won't happen again.

Pardon the blast from the past. Anyone remember the leopard spots seen along some of the groves imaged during the earlier flybys?

http://www.ciclops.org/view_media.php?id=4783

Could they be related to the jets, perhaps being the sources of jets in the distant past when they emerged from a different part of the moon?

I doubt it. I suspect they are more related to the rough topography, outcrops or boulders, than with cryovolcanism.