No ocean on Enceladous?

robnissen · Dec 17, 2007

A recent study has found no sodium in the plumes from Enceladous. The study concludes, therefore, that the plumes do not come from an ocean on Enceladous. http://news.bbc.co.uk/2/hi/science/nature/7145530.stm There have been several emails on this study in the enceladousfocus email list. Apparantly, there is no disagreement on the data, i.e., there is no sodium there, only on the interpretation. One poster noted that If the heat source is a collision with a coorbital, one would not expect the melt to be salty at all. So liquid water is still a possibility for the source of the plumes. It will be interesting how this shakes out.

robnissen · Dec 17, 2007

Below is an entire email from John Cooper at NASA to the Enceladous Focus group. (From my standpoint as an amatuer, I love being able to watch these scientific debates occur in real time.) Lack of detectable sodium either means there is no sodium in the upper ice crust of Enceladus or that the sodium is in a form not easily detectable by the observation that requires it to be in the form of an atomic vapor. Unlike Europa, the sodium does not appear in the form of a salt (Na2SO4 hydrated with H2O) on the surface, so there is no surface source to form the atomic vapor via sputtering effects of energetic particles from Saturn's magnetosphere. There could also be a difference in the magnetospheric particle population from that of Jupiter that makes sputtering much less effective than at Europa. The lack of Europa-like salts on the surface says that these salts are not coming out of the plumes, so salts apparently play no significant role on lowering the freezing temperature of the subsurface environment that the plume material orginates from. However, we could still have liquid subsurface reservoirs if sufficient ammonia or some other antifreeze compound was present and mixed in the water to maintain for ammonia a temperature of 173 Kelvin (-100 degrees Centigrade), or if there were heat sources to keep pure water at 273 Kelvin (0 degrees Centigrade). Even if the antifreeze and heat sources are not now present, these sources might have been more active in the recent past, and the current plume activity might be from the residual liquid from a recent source activity episode. Like the water geyser of Old Faithful in Yellowstone National Park, there could be cyclic episodes of antifreeze and heat source activity that accumulate energy to drive briefer episodes of plume activity as we now see. There are a number of very different ideas, including my own, that attempt to account for

brellis · Dec 17, 2007

There are a number of very different ideas, including my own, that attempt to account for the plume activity, with or without subsurface liquids, and the current debate involves much theoretical speculation. More measurements of the plume chemical composition and activity from an extended Cassini mission should help. It's understandable for scientists to want to spin the data in such a way to encourage mission extensions for Cassini and future missions. It's sad that a "No Oceans" headline might discourage further exploration, but that's the world we live in right now. I keep thinking about a Cassini-size mother ship with many nano-landers in a flexible mission scenario. Imagine if Cassini had dozens of mini-Huygens devices on board when the geysers were discovered - they could drop one into a Tiger stripe and see what's inside! <div class="Discussion_UserSignature"> I'm a recovering optimist - things could be better. </div>

bearack · Dec 17, 2007

I'm confussed (easily done). The artical states that there was no sodium but, the plumes were still of pure water. Wouldn't that still lead to an ocean then? <div class="Discussion_UserSignature"> <img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /> </div>

MeteorWayne · Dec 17, 2007

No, because it is too cold. It would be ice, not an ocean. <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>

JonClarke · Dec 17, 2007

It's understandable for scientists to want to spin the data in such a way to encourage mission extensions for Cassini and future missions. It's sad that a "No Oceans" headline might discourage further exploration, but that's the world we live in right now. Science is not about "spin", but about the best interpretation of the data. 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>

JonClarke · Dec 17, 2007

"Shakes out" indeed! <img src="/images/icons/wink.gif" /> Another possibility is that there is an ocean, but it is not in contact with rock, that there is a layer of dense ice between the ocean and the rocky core. 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 · Dec 17, 2007

Jon, That would be possible. I think if Enceladaus had an "off-center" core, then this would create a lot of tidal stress in the ice blanket swaddling the core, especially in the ice antipodal to the center of the core mass offset location, causing a localized warm pocket there. I am still waiting to see a close-pass flyby trajectory analysis to see if Enceldaus' mass distribution is symmetrically uniform, or not. As you may remember, I have been predicting we will find that its mass distribution is substantially asymmetric. So I view the non-observation of sodium as consistent with my proposal. Alternatively, if the source of Enc's water is frictional warming along fissure and fracture lines cause by gravitational tidal stress and perhaps a recent 'flip' sideways, then this warming mechanism also does not require contact with a rocky core, and the water could be sodium free. This mechanism was proposed in a recent paper, as you know. This too is consistent with non-observation of sodium. However, if the source of Enc's internal heat engine is radiogenic, then I would expect the water pocket to be touching exposed rock. In this case, the water pocket should contain sodium. This is inconsistent with observation, decreasing the likelyhood that Enc's internal engine is radiogenic. <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 · Dec 17, 2007

All good possibilities. Which is why it is a little early to be talking about dedicated missions, IMHO! I don't know enough to design a dedicated mission - or even whether it is worth 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>

3488 · Dec 17, 2007

Hi silylene, I would expect new information on this when Cassini buzzes by Enceladus on Wednesday 12th March 2008 @ a distance of only 24 KM / 14 miles. The Cassini spacecraft is to pass through the plumes & also to map the gravity well of Enceladus. Ths will reveal if Enceladus is differentiated & if so, would reveal if the core is asymmetric. If so, I would expect the mass concentratation to be pointing at Saturn, with Tethys & Dione tugging on it (much like Europa, Ganymede & Callisto on Io in Jupiter's system). However, this does not explain the geyser acitivty being concentrated around the antarctic region of Enceladus & why the gashes are concentrated there, yet the northern region of Enceladus is far 'older' with a large number of impact craters. Therefore the core of Enceladus if lopsided, will be concentrated in the southern hemisphere. The problem with that, is that Saturn's gravity should tilt Enceladus again, to bring that 'lump' in line. The lack of sodium in the plume does fit in with the posibilty that the warming is not radiogenic & is thus tidally induced, possibly with Tethys & Dione. Or perhaps Enceladus was impacted relatively recently, the Tiger Stripes are freshly frozen ice & the geysers, heat still being released. 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 · Dec 17, 2007

Hi Jon, I think we will have that answer next March. <img src="/images/icons/laugh.gif" /> It will be a very difficult but a fantastically close approach. I think the very closest approach will be fields, particles & multispectral data, as the encounter speed will be too great for clear images, but during the approach & just afterwards, the sharpest images yet of Enceladus will be obtainable. <img src="/images/icons/laugh.gif" /> This reminds me of the Galileo Spacecraft & the Thor Volcano on Io. <img src="/images/icons/laugh.gif" /> 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>

h2ouniverse · Dec 17, 2007

To me this is a logic step too far. No salt detected in the plume. OK so this may mean that the plume does not come from an ocean . That does not mean there is no ocean.... There are many theories explaining that particles come from abrasion from ice walls in the cracks, or that they are secondary emission. Particles extracted from the shelf should contain no salt: the freezing process differentiates the water (and tend to concentrate salt btw in the liquid layer beneath). In terms of exploration strategy this is certainly important (is it interesting to put a robot analyzing the vents if they do not come from an underground ocean?). But to conclude there is no water is going too far imho. The only certainty is that there is far more heat energy in Enceladus than thought few years ago. And very little flux is needed to keep a layer liquid at rock / shelf interface (few hundredth of W/m2). May be the flux is just low enough for water to be absent, and high enough for cracks to appear. May be.

alokmohan · Dec 18, 2007

We should not want ocean to suit our desire.Lus be dispassionate.

robnissen · Dec 18, 2007

Here is another article on the lack of sodium in the Enceladous plumes: http://www.saturndaily.com/reports/Hot_Spot_On_Enceladus_Causes_Plumes_999.html More interesting to me than the article, however, is this email discussion between Dr. Porco and Dr. McKinnon regarding his comments in the article: Dr. Porco: > I'm very surprised Bill would say this, when in fact /> I came away with /> entirely the opposite impression: that you HAVE to /> have liquid /> *somewhere* in Enceladus to get enough tidal flexing /> to cause any /> significant amount of heating, which almost /> certainly has a tidal source. Dr. McKinnon: This is, alas, a news report based on a press release based on an abstract & interview, so some things have gotten somewhat garbled. I certainly do not claim that we have no evidence at all for an ocean. In fact I said the very opposite in my AGU talk and abstract. I also said in my abstract the absence of Na puts severe constraints on any direct derivation of the plumes from boiling water. This is certainly true. There should have been a bridge clause, after the "is there life remark?," that made it clear I was talking about the (C)old Faithful concept specifically. The end of the paragraph ("no boiling or venting") refers to whether the ocean is revealing itself chemically (as Misha put it in a different email). I should have paid greater attention to the final wording of the press release, in the runup to the AGU. Mea culpa. Dr. Porco: /> /> And given the vigorous dispute over the /> interpretation of the Na /> non-detection, it's not at all clear that just

h2ouniverse · Dec 18, 2007

To Borman and Alokmohan, I posted at 1am after a 18-hour working day. I did not realize my tone was overly aggressive and corrected my post accordingly. This being said, Rob's post tends to confirm what I expressed. These times, Jupiter and Saturn are in competition among the scientists (to get a space mission) so we should take care of scoops.... Best regards.

alokmohan · Dec 19, 2007

Never mind.I dont want ocean in enceladus.

h2ouniverse · Dec 19, 2007

hi AM, you said "I dont want ocean in enceladus". Why? Water-frustrated regards

alokmohan · Dec 20, 2007

There are too many oceans,none in habitable place.

bearack · Dec 20, 2007

We don't know anything about them yet. I would rather investigate water than rock. <div class="Discussion_UserSignature"> <img id="06322a8d-f18d-4ab1-8ea7-150275a4cb53" src="http://sitelife.space.com/ver1.0/Content/images/store/6/14/06322a8d-f18d-4ab1-8ea7-150275a4cb53.Large.jpg" alt="blog post photo" /> </div>

robnissen · Dec 20, 2007

An article that will be probably be published in January in Nature makes a pretty compelling case that the plumes are formed from liquid water. In particular, the article notes, that based on the momentum of the ice particles, they must be ejected at, at least, 250K which probably means the particles are liquid. Below is a snippet from an email from the author discussing his upcoming article: At low temperatures a dilute gas becomes inefficient at transferring momentum to the ice particles. We show that temperatures around 250K or higher, at the location of gas formation are consistent with the observed particle fluxes, suggesting evaporation from liquid or very warm ice. Our paper has been accepted for publication in Nature and will probably appear in January./safety_wrapper>

No ocean on Enceladous?

robnissen

Guest

robnissen

Guest

brellis

Guest

bearack

Guest

MeteorWayne

Guest

JonClarke

Guest

JonClarke

Guest

silylene old

Guest

JonClarke

Guest

3488

Guest

3488

Guest

h2ouniverse

Guest

alokmohan

Guest

robnissen

Guest

h2ouniverse

Guest

alokmohan

Guest

h2ouniverse

Guest

alokmohan

Guest

bearack

Guest

robnissen

Guest

Similar threads

TRENDING THREADS

Latest posts

Share this page