Sodium not detected, looks bad for an ocean under that ice.NASA's still considering sending a dedicated mission to Enceladus, but I think that it shouldn't come before a mission to Europa. That still has the best possibility of an ocean under all the ice (and thus life).

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The ice shell around Europa should be opened only with great caution. I suspect Pandora's box on steroids. Still, I'm all for opening the box and those of Ganymede and Callisto as well.

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All these worlds are yours, except Europa, attempt no landings there.

Can not fresh water lakes be long lived?

Bob Clark

Not compared to an ocean. But the sodium expectation is based on the assumption of liquid water in direct contact with the rock-- a thick layer of ice (or some other substance) at the ocean bottom might prevent this. Arctic and Antarctic seas on Earth sometimes develop ice on the bottom, I believe, so it's possible.

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Lakes are open systems with respect to salts, oceans much less so. In fact you have to actively remove salts from the oceans otherwise the oceans would be like the Dead Sea, a supersaturated brine.

Jon

Okay, now we are mixing Enceladus and Europa. To return to the OP, there are a few papers trying to explain what is happening at Enceladus.

In GRL there is this paper about why salt may not come out even though it is there.

And in Physics Today of October 2007, there was this paper about Clathrate Hydrates Under Pressure, which might have something to do with Enceladus' plume.

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Optimism does not change the laws of physics. (T'Pol)
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Europa was mentioned in the OP. It relates to the topic of where to send a probe.

__________________
"If this were play'd upon a stage now, I could condemn it as an improbable fiction."
Shakespeare, Twelfth Night
Illuminati's Razor-The most complicatedly evil answer is usually the most correct answer. - Fazor
"Every book is a children's book if the kid can read." - Mitch Hedberg
"Distance doesn’t matter much in space, where if you just start a thing off with the right kind of shove, sooner or later it will get where you want it to go." -Frederik Pohl, Mining the Oort

You are right! Bad case of quick reading :-)

ESA is planning a 2 spacecraft mission called LaPlace that will send a mother orbiter to Jupiter and a daughter orbiter around Europa. At the moment no landers are planned but who knows what might happen between now and 2019.

__________________
************************************************** *************************
Optimism does not change the laws of physics. (T'Pol)
A good scientist has freed himself of concepts and keeps his mind open to what is. (Dao De Jing 27)
************************************************** *************************
Martin ( http://www.geocities.com/DrMartinV )

If Enceladus has an extremely thick crust of ices, and tidal forces cause warming just below the surface, then a subsurface ocean or lakes with an ice floor and an ice roof may exist.
A journey to the centre of Enceladus,
A crust of 0.5 to 1 or 2 km thick, several km of liquid, several hundred km of solid ices, then the rocky core.
Although reality will probably be just outright bizarre.
There has been an assumption that immediately below the ocean and in contact with it are salt bearing rocks.
Maybe there is no ocean or lakes at all.
Perhaps the fluids are ejected and squeezed out as soon as liquid is formed in the fissures and cracks. With nothing more than a few underground creeks and rivers.

??

Is Callisto not a target for investigation?
There is a huge scar on Callisto, which (to me anyway), says,
"Hi, I have a thick icy crust and a liquid ocean below, see where a big asteroid hit me, I swallowed it up, and healed my injury."

If someone could enlighten me as to the features name, I would be grateful.

See this link,
http://www.planetary.org/blog/article/00001264/

from this discussion,
New Views from Galileo

or just look at the pic on the Planetary Society site.




Credit: NASA / JPL / Ted Stryk

Not sure if it was the right thing to post that link to the image on the Planetary Society website, perhaps I should have copied the pic, put it on my own site, then linked to it. You know, some folks protect their bandwidth.
Kev.

And no soup for you! ;-)

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Laplace, not LaPlace , named after a famous french mathematician if I'm not mistaken.

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You are right Zach, and as a member of the Laplace team I should have know how to spell it!

__________________
************************************************** *************************
Optimism does not change the laws of physics. (T'Pol)
A good scientist has freed himself of concepts and keeps his mind open to what is. (Dao De Jing 27)
************************************************** *************************
Martin ( http://www.geocities.com/DrMartinV )