Underground Water Reservoirs Power Geysers on Enceladus
Written by Nancy Atkinson
Enceladus geyser. Credit: NASA/JPL
Saturn's moon Enceladus may indeed hide an underground reservoir of water. Scientists analyzed the plumes seen spewing from the moon with the Cassini spacecraft, and found water vapor and ice. "There are only three places in the solar system we know or suspect to have liquid water near the surface," said Joshua Colwell Cassini team scientist from the University of Central Florida. "Earth, Jupiter's moon Europa and now Saturn's Enceladus. Water is a basic ingredient for life, and there are certainly implications there. If we find that the tidal heating that we believe causes these geysers is a common planetary systems phenomenon, then it gets really interesting."
Using data from Cassini's Ultraviolet Imaging Spectrograph (UVIS), the team's findings support a theory that the plumes observed are caused by a water source deep inside Enceladus. An Earth analog is Lake Vostok in Antarctica, where liquid water exists beneath thick ice.
Scientists suggest that in Enceladus's case, the ice grains would condense from the vapor escaping from the water source and stream through the cracks in the ice crust before heading into space. That's likely what Cassini's instruments detected in 2005 and 2007, the basis for the team's investigation.
The team's work also suggests that another hypothesis is unlikely. That theory predicts that the plumes of gas and dust observed are caused by evaporation of volatile ice freshly exposed to space when Saturn's tidal forces open vents in the south pole. But the team found more water vapor coming from the vents in 2007 at a time when the theory predicted there should have been less.
Instead, their results suggest that the behavior of the geysers supports a mathematical model that treats the vents as nozzles that channel water vapor from a liquid reservoir to the surface of the moon. By observing the flickering light of a star as the geysers blocked it out, the team found that the water vapor forms narrow jets. The authors theorize that only high temperatures close to the melting point of water ice could account for the high speed of the water vapor jets.
Although there is no solid conclusion yet, there may be one soon. Enceladus is a prime target of Cassini during its extended Equinox Mission, underway now through September 2010. Cassini launched from the Kennedy Space Center in 1997 and has been orbiting Saturn since July 2004.
The team's findings are reported in the Nov. 27 issue of the journal Nature.
Source: EurekAlert
Filed under: Saturn
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November 26th, 2008 at 1:21 pm
Saturn's moon Enceladus may indeed hide an underground reservoir of water.
The important word here is may. Doesn't that make the title of this article factually incorrect?
November 26th, 2008 at 1:32 pm
One must recall that there was no prediction of tidally induced expulsion of water from Enceladus, based on its small size. There is nothing on Enceladus, in the recent extreme closeups of the expulsion source, that resembles a geyser. Nozzles diverge their output, which then expands into vacuum, without collimation. This all points to plasma sputtering as a current impinges on the surface of Enceladus. Saturn is a known energetic charged particle environment. The temperature of Enceladus' surface is 70 degrees F above absolute zero; this is a moon in a very deep freeze and it's hard to imagine the level of heat required to bring the ice in the interior up to our room temperature. The article does not mention that a priori calculations do not support this level of tidal heating.
November 26th, 2008 at 2:11 pm
"The temperature of Enceladus' surface is 70 degrees F above absolute zero; this is a moon in a very deep freeze and it's hard to imagine the level of heat required to bring the ice in the interior up to our room temperature."
OK but the surface of the earth is quite cool compared to plumes of magma, Isn't there always a temperature gradient as you go below the surface.
November 26th, 2008 at 2:43 pm
A sputtering effect strong enough to cause the the observed plumes and structure would require a strong magnetic field (or negatively charged region ) over the south pole of enceladus to concentrate the ions in saturns vicinity onto the vent locations. Cassini carries a magnetometer and radio science instruments, and not a hint of such a field or charge anomaly has been detected. Such a current would also have an effect of its own on saturns magnetosphere, and the only effect detected is that best explained by ions leaving enceladus and being dragged along by saturns magnetic field. It's also very difficult to imagine how enceladus could generate a strong magnetic field or charged spot, even harder than to see why it should be warm on the south pole!
November 26th, 2008 at 3:50 pm
Any explanation, such a tidal heating; that does not also explain why the other, similar sized moons in similar orbits (such a Dione) do not exhibit evidence of the same phenomenon. This is just a guess, an admission no one seems to have come up with a good idea of what else could cause this…yet.
November 26th, 2008 at 8:20 pm
Big water table under there for sure. Bank it.
November 26th, 2008 at 9:56 pm
Jerry, what did you say? Your "guess" is an incomplete sentence. Just interested in what people would like to say.
I'm going with the underground reservoir theory although I too, was dissappointed with the lack of obvious exit points apparent in pretty dang good pics!
November 26th, 2008 at 10:57 pm
Bill,
If this was plasma that would pretty much negate there being detected water/ice now wouldn't it?
November 27th, 2008 at 12:33 am
That's very interesting. But I'm curious about the basic ingredient for life. Can there some kind of 'life' form that doesn't need water? Just like viruses… but more 'intelligent'.
November 27th, 2008 at 4:30 am
You know what really makes me laugh? Everyone is so intrested in finding water elsewhere in the universe. H2O is probably one of the most abundant molecule in the universe. Most places already have an overwelming amount of hydrogen. With other places it's nitrogen. The ingrediant thats seems to be scarce is the element oxygen. Why is oxygen the one that is so scarce to find on other worlds and their orbiting companions? Hasn't anyone else ever noticed this?, or is it just me? Even methane and ammonia is more abundant it seems then oxygen. I find it a little hard to believe that one element so important would be so scarce to find. So I guess my question is, Where's the Oxygen? Maybe we should be looking for oceans of frozen or liquid oxygen somewhere out there on those frigid worlds. I would believe we would be more apt to find oxygen in the elemental state more then in the moleiculer state with hydrogen. Once found, it would be as simple as combining the two to MAKE water. Why not just send a lander there and find out instead of guessing at it?
November 27th, 2008 at 5:30 am
Ross,
Oxygen is very reactive. It is very hard to find it in its pure, molecular form, since it is almost always bound to some other element.
It is abundand here on Earth because it is always being replenished by the photosynthetising plants.
I doubt we will ever find a liquid oxygen ocean anywhere.
November 27th, 2008 at 9:07 am
Lets say for a moment there is an ocean why is it always assumed that the water is habitable it could be very heavy with acids and other chemicals making it almost impossible for anything to live there. Water may mean life here but what of other planets and there enviroments.
November 27th, 2008 at 9:17 am
Carbon is the key to life, so watch for CO2 and methane (CH4), both are abundent on all the planets and their moons. Only carbon can has a chemistry that is complex enough to support life. The solvent should make little difference, be it water, or the ethane lakes of Titan, but it will make a HUGE difference in life forms. Life will be found on the icy moons, especially Titan. But it will be VERY different then life on Earth. I predict a debate on whether it is actually "alive" or not.
November 27th, 2008 at 10:38 am
That is a fascinating theory – that we could find a life form which was completely chemically incompatible with us. We may find microbial life on some of these moons, but I suspect some general warmth is also necessary for development. Perhaps flesh and bone is only possible in a warm water-carbon-oxygen world. Could there really be a warm ethane-carbon-methane form adequate for complex reactions which could produce some kind of living tissue? How would the basic chemistry work?
November 27th, 2008 at 7:38 pm
"Any explanation, such a tidal heating; that does not also explain why the other, similar sized moons in similar orbits (such a Dione) do not exhibit evidence of the same phenomenon.?
Could the others simply have drier interiors?
November 27th, 2008 at 8:24 pm
Like the bacteria that exists here on earth in total darkness. No sunlight no water and yet they exist, couldn't the same be happening on other planets or moons? and if they do exist can we call it life or just the precursor to it?
P.S.
I agree the things we find on these moons and planets might be technically called life but they'll be far from alive.
November 28th, 2008 at 10:47 am
Clarifying:
Tidal heating was not expected to be significant on this size of moon. It has been adopted as the 'most logical' candidate because the mass/density of this moon is too small to reasonably suggest other possible solutions such as a uranium core.
'Tidal heating' is not a differentiated explanation: Why Enceladus, and not the other icy moons of similar compositions? Why near one pole, but not the other?
Gravitational data (from Cassini) may eventually provide information, such as crustal distortion, that is consistent with a tidal model, but for now, the best answer is that the cause of these geysers is a mystery.
November 28th, 2008 at 5:26 pm
Now to find a fish or two in the plumes… Seriously though, instead of drilling through perhaps km of ice to take a sample, could we send a probe to collect and analyce the Europa and Encaladus plumes?
December 1st, 2008 at 8:02 am
Thanks for comments. The other moons are being seen to exhibit similar behaviors. Plasma can be composed of any ionized species including water. The moon need not have an intrinsic mag field to act as a node in a circuit, its resistance to a charged particle flux is less than that of vacuum. I also note a paper abstract from 2007 that defies the idea of tidal heating:
"Tidal heating in Enceladus
Jennifer Meyer and Jack Wisdoma,
Massachusetts Institute of Technology, Cambridge, MA
Abstract:
The heating in Enceladus in an equilibrium resonant configuration with other saturnian satellites can be estimated independently of the physical properties of Enceladus. We find that equilibrium tidal heating cannot account for the heat that is observed to be coming from Enceladus. Equilibrium heating in possible past resonances likewise cannot explain prior resurfacing events.