Latest from Enceladus

[MattEU]

Cassini satellites E8 flyby of Saturn's moon Enceladus

[solrey]

This image is quite interesting.


click image for full res

Are those concentric rings just camera artifacts or are they real? Reminds me of the light wave interference pattern seen when doing a star test collimation on a reflector telescope.





Not sure what, if anything, that means right now. If not artifacts, could they be some kind of EM wave interference pattern from a discharge event?

[mharratsc]

Looks like a blurred double-image taken through a camera with raindrops failing on the lens... o.O

It will be interesting to see what NASA says about that one, or if they say that it was just 'corrupt' and they delete it or something

Mike H.

[GaryN]

That is a really strange image, solrey. I went and had a look at the site, no information other than that the imager was using 2 clear filters.

If not artifacts, could they be some kind of EM wave interference pattern from a discharge event?

I'd consider something like that. The distinct hexagon nature of some of the features would suggest a magnetic influence.

Looks like a blurred double-image

That was my first impression Mike, but under close examination that doesn't seem to hold up, different spacing between what appear to be similar features. Being a one-off type of image I guess they would say a defective image. Worth an e-mail to see if they have an explanation though. Odds of an answer?

[solrey]

Here's another example of wave interference patterns



I tried to reason that it may just be an overmagnified out of focus image that produces those interference patterns around bright points on the surface, but there are so many and some are in the darker area to the left.

They were focusing on the plume region during this flyby. Makes me wonder if it's like looking down the barrel of some weaker plume "jets" showing icy grains in the exosphere "polarized" by an EM interference pattern. The other images of the jets in silhouette shows many small round jets along a couple of lines in the shadowed side of the terminator. The layout, mostly in lines, of those concentric patterns seems to fit the pattern of some of those jets in silhouette.

I don't believe that kind of interference pattern happens in refractive optics, and I'm guessing that the camera's lens is a simple and stable refractive optic system, as opposed to more complicated and sensitive reflecting optics.
Anyways, it would be interesting to see an explanation from jpl.

[nick c]

hi solrey,

It has got to be a camera artifact. I think your close with the reflector telescope collimation star test, I thought that it was a [url2=http://wyant.optics.arizona.edu/fresnelZones/fresnelZones.htm]circular aperature diffraction pattern[/url2].
The lenses used are both refractor and reflector:

Wide Angle Camera [WAC](20 cm f/3.5 refractor; 380-1100 nm; 18 filters; 3.5ox3.5o)
Narrow Angle Camera [NAC](2 m f/10.5 reflector; 200-1100 nm; 24 filters; 0.35ox0.35o)

http://saturn.jpl.nasa.gov/spacecraft/c ... assiniiss/

Found this on the FAQ page:

What are those dark donut shapes?

Small donut-like dark spots in images are actually out of focus dust specks on the filter wheels, lenses or other parts of the optics of the cameras. Because there is no way to clean the cameras in space, more of these spots may appear as the Cassini mission progresses.

http://saturn.jpl.nasa.gov/faq/FAQRawImages/#q7

Nick

[solrey]

Thanks nick, missed those faq's.

That makes sense if the camera was the reflector under high mag (it was taken at 510,000 km) and the dust specks were catching some glare from the light of the sun hitting the lens at a high angle as seems to be the case here.
Normally wouldn't even be noticeable though.

Kewl, the mirrors appear to have maintained near perfect alignment. It's likely some version of a Cassegrain design.

That would actually be a decent way to keep tabs on the mirrors alignment and correct if they can be adjusted with little servo's.

[Wanderer]

Nasa's Explanation of Enceladus

Giant plumes of ice have been photographed in dramatic fashion by the robotic Cassini spacecraft during this past weekend's flyby of Saturn's moon Enceladus. Pictured above, numerous plumes are seen rising from long tiger-stripe canyons across Enceladus' craggy surface. Several ice jets are even visible in the shadowed region of crescent Enceladus as they reach high enough to scatter sunlight. Other plumes, near the top of the above image, appear visible just over the moon's sunlit edge. That Enceladus vents fountains of ice was first discovered on Cassini images in 2005, and has been under close study ever since. Continued study of the ice plumes may yield further clues as to whether underground oceans, candidates for containing life, exist on this distant ice world.

From an EU perspective might this not show Electrical Activity carving out the canyons??

[redeye]

From Cassini Website

As the Crust Turns: Cassini Data Show Enceladus in Motion

January 11,2010


--------------------------------------------------------------------------------
[ - ] Text [ + ]

Cassini captured this mosaic on Oct. 5, 2008, just after coming within 25 kilometers (15.6 miles) of the surface of Enceladus.
Blobs of warm ice that periodically rise to the surface and churn the icy crust on Saturn’s moon Enceladus explain the quirky heat behavior and intriguing surface of the moon’s south polar region, according to a new paper using data from NASA’s Cassini spacecraft.
“Cassini appears to have caught Enceladus in the middle of a burp,” said Francis Nimmo, a planetary scientist at the University of California Santa Cruz and a co-author of the new paper in Nature Geoscience. “These tumultuous periods are rare and Cassini happens to have been watching the moon during one of these special epochs.”

The south polar region captivates scientists because it hosts the fissures known as “tiger stripes” that spray water vapor and other particles out from the moon. While the latest paper, released on Jan. 10, doesn’t link the churning and resurfacing directly to the formation of fissures and jets, it does fill in some of the blanks in the region’s history.

“This episodic model helps to solve one of the most perplexing mysteries of Enceladus,” said Bob Pappalardo, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., of the research done by his colleagues. “Why is the south polar surface so young? How could this amount of heat be pumped out at the moon’s south pole? This idea assembles the pieces of the puzzle.”

About four years ago, Cassini’s composite infrared spectrometer instrument detected a heat flow in the south polar region of at least 6 gigawatts, the equivalent of at least a dozen electric power plants. This is at least three times as much heat as an average region of Earth of similar area would produce, despite Enceladus' small size. The region was also later found by Cassini’s ion and neutral mass spectrometer instrument to be swiftly expelling argon, which comes from rocks decaying radioactively and has a well-known rate of decay.

Calculations told scientists it would be impossible for Enceladus to have continually produced heat and gas at this rate. Tidal movement – the pull and push from Saturn as Enceladus moves around the planet – cannot explain the release of so much energy.

The surface ages of different regions of Enceladus also show great diversity. Heavily cratered plains in the northern part of the moon appear to be as old as 4.2 billion years, while a region near the equator known as Sarandib Planitia is between 170 million and 3.7 billion years old. The south polar area, however, appears to be less than 100 million years old, possibly as young as 500,000 years.


These drawings depict explanations for the source of intense heat that has been measured coming from Enceladus' south polar region. These models predict that water could exist in a deep layer as an ocean or sea and also near the surface.
Craig O’Neill of Macquarie University in Sydney, Australia, and Nimmo, who was partially funded by the NASA Outer Planets Research program, adapted a model that O’Neill had developed for the convection of Earth’s crust. For Enceladus, which has a surface completely covered in cold ice that is fractured by the tug of Saturn’s gravitational pull, the scientists stiffened up the crust. They picked a strength somewhere between that of the malleable tectonic plates on Earth and the rigid plates of Venus, which are so strong, it appears they never get sucked down into the interior.
Their model showed that heat building up from the interior of Enceladus could be released in episodic bubbles of warm, light ice rising to the surface, akin to the rising blobs of heated wax in a lava lamp. The rise of the warm bubbles would send cold, heavier ice down into the interior. (Warm is, of course, relative. Nimmo said the bubbles are probably just below freezing, which is 273 degrees Kelvin or 32 degrees Farenheit, whereas the surface is a frigid 80 degrees Kelvin or -316 degrees Farenheit.)

The model fits the activity on Enceladus when the churning and resurfacing periods are assumed to last about 10 million years, and the quiet periods, when the surface ice is undisturbed, last about 100 million to two billion years. Their model suggests the active periods have occurred only 1 to 10 percent of the time that Enceladus has existed and have recycled 10 to 40 percent of the surface. The active area around Enceladus’s south pole is about 10 percent of its surface.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.

Cheers!

[solrey]

Given the plasma environment around Saturn and the fact that there are field aligned ion beams propagating from Saturn into the "geyser" region of Enceladus, it makes sense to consider the source of these "geysers" to be the electromagnetic plasma environment ripping ions and other material from the icy surface. No liquid required.

Evidence For Enceladus Link To Saturn Ionosphere: Does The Plume Have An Auroral Footprint?

It is increasingly well accepted that, despite its diminutive size, the tiny icy moon Enceladus is the dominant source of water group neutrals and charged particles throughout Saturn's magnetosphere through the copious gas and dust emanations from its South pole. During two recent Cassini flybys the spacecraft plasma instruments were oriented such that they looked along a magnetic flux tube nominally connecting the Enceladus plume to Saturn's ionosphere. Two of the remarkable discoveries from these observational campaigns were, 1) high energy (10s-100s of keV) field aligned ion beams propagating from Saturn toward the plume and 2) lower energy field aligned electron beams which were observed to 'flicker' in energy from 10s of eV to several 100 eV. Initial speculation was that this is evidence of an Alfven wing type interaction, such as exists at Io due to significant mass loading in the wake of the moon. It was subsequently realised that the magnetic field signature is not consistent with this simple picture, leading us to speculate that there exists a more filamentary Birkeland current system with the observed variability linked to the highly dynamic and variable nature of the Enceladus outgassing. Ions could be accelerated by wave activity or field-aligned potential drops just above the ionosphere, but we have yet to ascertain if either is sufficient to explain the observed very high energy ion beams. Additionally we will show that similar phenomena exist near the L-value of Enceladus, but away from the moon - implying the existence of a significant extended Enceladus plasma torus.

That's a step in the right direction by at least acknowledging Birkeland currents, an extended plasma torus, and ion beams but they are still reversing cause and effect so remain stuck on a mechanical explanation as the cause of Enceladus plumes.

[jjohnson]

One has to wonder how many lava lamps these guys have observed generating sufficient pressure to create high velocity ionized discharges hundreds of kilometers into space. All the forces are right there in front of them (too), to do just what is observed, from their own instruments and cameras. All the artistic pictures and cutaways can't cover up the fact that gravity, temperature and pressure differentials, and tidal forces simply are not capable of generating the same degree of forces that charge differentials and high amperage current sheets can in accelerating mass this far out above this moon. Enceladus is not an isolated example in this respect, either. In fact, it is behaving a little like a more or less steady state comet fed by Saturn's continuously electrically active environment, is it not?

[mharratsc]

Did anyone see the movie 'Monsters Vs. Aliens'?

There's a part where the General starts talking about how super secret his 'monster' base is, and this one scientist says "What- like Area 51?" whereupon he gets shot in the neck with a dart by a hidden sniper and he slumps under the table unconscious...

I imagine that something like that would happen to these scientists if they just came out and said "The EU guys were right because we've discovered..." *Thwap!* (under the table he goes)... Then some other obsequious putz with a receptive wallet would take his place quickly and state "It was gravity! We swear!! We'll have a formula for you by the end of the week. Move along now! Nothing to see here..."

[MGmirkin]

Evidence For Enceladus Link To Saturn Ionosphere: Does The Plume Have An Auroral Footprint?

It is increasingly well accepted that, despite its diminutive size, the tiny icy moon Enceladus is the dominant source of water group neutrals and charged particles throughout Saturn's magnetosphere through the copious gas and dust emanations from its South pole. During two recent Cassini flybys the spacecraft plasma instruments were oriented such that they looked along a magnetic flux tube nominally connecting the Enceladus plume to Saturn's ionosphere. Two of the remarkable discoveries from these observational campaigns were, 1) high energy (10s-100s of keV) field aligned ion beams propagating from Saturn toward the plume and 2) lower energy field aligned electron beams which were observed to 'flicker' in energy from 10s of eV to several 100 eV. Initial speculation was that this is evidence of an Alfven wing type interaction, such as exists at Io due to significant mass loading in the wake of the moon. It was subsequently realised that the magnetic field signature is not consistent with this simple picture, leading us to speculate that there exists a more filamentary Birkeland current system with the observed variability linked to the highly dynamic and variable nature of the Enceladus outgassing. Ions could be accelerated by wave activity or field-aligned potential drops just above the ionosphere, but we have yet to ascertain if either is sufficient to explain the observed very high energy ion beams. Additionally we will show that similar phenomena exist near the L-value of Enceladus, but away from the moon - implying the existence of a significant extended Enceladus plasma torus.

That's a step in the right direction by at least acknowledging Birkeland currents, an extended plasma torus, and ion beams but they are still reversing cause and effect so remain stuck on a mechanical explanation as the cause of Enceladus plumes.

Good catch on that paper... Goes right alongside the Peratt / Dessler paper on filamentation of Io's Volcanoes, etc. Which makes sense in light of the [now] old news release on Io's radio road and electric currents over its "volcanoes."

(Filamentation of Volcanic Plumes on the Jovian Satellite Io)
http://plasmascience.net/tpu/downloads/ ... essler.pdf

(Jupiter's Io Generates Power and Noise, But No Magnetic Field)
http://www.spaceref.com/news/viewpr.html?pid=6849

Galileo detected electrical currents flowing along magnetic field lines above two areas of volcanic activity on Io, Kivelson said. Material shot high from eruptions is apparently affecting conductivity more than 100 kilometers (about 60 miles) above the surface.

"If this is the mechanism that's producing the currents, it may help us in the search for active plumes," she said.

Granted they seem to think it's the volcanoes contributing conductive materials and thus causing the currents, rather than considering the possibility it's the currents impinging on the surface causing the "volcanoes"...

Might something similar be happening at Enceladus? Maybe not precisely the same. But I'd certainly consider the same possibility, especially in light of the paper you mentioned above.

Best,
~Michael Gmirkin

[solrey]

Thanks Michael. Good papers demonstrating commonality you cited there.
Went fishing and caught a couple more.

Negative ions in the Enceladus plume

During Cassini’s Enceladus encounter on 12th March 2008, the Cassini Electron Spectrometer, part of the CAPS instrument, detected fluxes of negative ions in the plumes from Enceladus. It is thought that these ions include negatively charged water group cluster ions associated with the plume and forming part of the ‘plume ionosphere’. In this paper we present our observations, argue that these are negative ions, and present preliminary mass identifications. We also suggest mechanisms for production and loss of the ions as constrained by the observations. Due to their short lifetime, we suggest that the ions are produced in or near the water vapour plume, or from the extended source of ice grains in the plume. We suggest that Enceladus now joins the Earth, Comet Halley and Titan as locations in the Solar System where negative ions have been directly observed although the ions observed in each case have distinctly different characteristics.

That compliments the data from the other paper regarding field aligned electron beams.

lower energy field aligned electron beams which were observed to 'flicker' in energy from 10s of eV to several 100 eV.

Flickering field aligned electron beams sounds like a relaxation oscillator to me.

And this on the chemistry:

Enceladus' plume: Compositional evidence for a hot interior

The combined observations of Saturn's moon Enceladus by the Cassini CAPS, INMS and UVIS instruments detected water vapor geysers in which were present molecular nitrogen (N2), carbon dioxide (CO2), methane (CH4), propane (C3H8), acetylene (C2H2), and several other species, together with all of the decomposition products of water. We propose that the presence of N2 in the plume indicates thermal decomposition of ammonia, and hence high temperatures in the interior of the moon (e.g., 500 to 800 K). Such an environment also appears to be suitable for the production of methane (CH4) from carbon monoxide (CO), or carbon dioxide (CO2). The presence of C2H2 and C3H8 strongly suggest that catalytic reactions took place within a very hot environment. The internal environment of Enceladus is inferred to be or have been favorable for aqueous, catalytic chemistry. This permits the synthesis of many complex organic compounds that could be detected in future Cassini observations.

Within a very hot wet environment, or a "warm" electric one full of energetic electrons and negative and positive ions?
The chemistry is much like that found in comet tails.

Electro-chemical and exothermic reactions are staring them right in the face yet they're still stuck on mechanical forces and geysers. And getting ever more wackadoodle in their ad-hoc guesses as they go.

Cheers

[solrey]

Fun with science.

The scenario.
The electron beams detected ranged from 10's of eV to several 100 eV.
Just 1 eV is equivalent to 11,604 degrees Kelvin (or about 11,331oC)
They assume the presence of N2 from thermal decomposition of ammonia NH3
That thermal decomposition of NH3 to N2 requires temperatures of 500-800 K
It requires a hot environment to produce C2H2 and C3H8 in their own words.
We'll be generous even, give them 1,000 K
And more generous still and assume an ion temperature an order of magnitude lower.
The lowest energy electron beam detected of 10 eV would equate to ion temperatures @(1eV) of 11,604 K
The low-midrange of 100 eV gives ion temps (@10eV) of 116,040 K
1 eV will accelerate an electron to 420 km/s
Or an ion to 0.021 km/s (100 eV would be 2.1 km/s or 7,560 km/h...or about twice the speed of a bullet.
Minimum.
You get the idea.
The thermal energy for the reaction is contained in the kinetic energy (expressed in eV) of the reacting elements via the electric field.
With lots of room to spare and accelerate ions to at or near "supersonic" (ion-acoustic) velocities.
And probably maintain critical ionization velocity for some.
Dust grains would be accelerated by the electric field significantly slower because they are much heavier than an ion, but have more charge also, so they'd still be pretty fast.

Slow dust in Enceladus' plume from condensation and wall collisions in tiger stripe fractures

One of the spectacular discoveries of the Cassini spacecraft was the plume of water vapour and icy particles (dust) originating near the south pole of Saturn's moon Enceladus. The data imply considerably smaller velocities for the grains than for the vapour which has been difficult to understand. The gas and dust are too dilute in the plume to interact, so the difference must arise below the surface. Here we report a model for grain condensation and growth in channels of variable width. We show that repeated wall collisions of grains, with re-acceleration by the gas, induce an effective friction, offering a natural explanation for the reduced grain velocity. We derive particle speed and size distributions that reproduce the observed and inferred properties of the dust plume. The gas seems to form near the triple point of water; gas densities corresponding to sublimation from ice at temperatures less than 260 K are generally too low to support the measured particle fluxes. This in turn suggests liquid water below Enceladus' south pole.

The Bohm sheath criterion in strongly coupled complex plasmas

In many experiments involving complex plasmas (under microgravity as well as in laboratory conditions), the particles are strongly coupled and remain in an equilibrium state, which results from a self-consistent distribution of all plasma parameters within the discharge. If the discussion is limited to the cases when the gravitational force is negligibly small (e.g. in microgravity experiments or when dealing with tiny, submicron/nanometer particles), we show that the strongly coupled structures, common to many experiments, allow us to introduce an effective `temperature' associated with the electrostatic interactions between similarly charged microparticles. Introducing such a `temperature', which is usually a few orders of magnitude higher than the real kinetic dust temperature, permits us to reduce the problem to the standard scheme of a Sagdeev potential. Using the small-potential expansion approach of Bohm, we obtain results that can significantly modify the classical requirement that the ion velocity exceeds the ion-acoustic speed at the sheath edge