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Enceladus Plume Search, Nov. 27
jmknapp
post Nov 24 2005, 04:01 PM
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Interesting item in the science plan kernel (S16) just released to the NAIF website:

OBSERVATION_ID: S1629

SEQUENCE: S16

OBSERVATION_TITLE: Plume Search

SCIENCE_OBJECTIVE: Hope to detect/observe plumes, whether from volcanic activity or geysers.

OBS_DESCRIPTION: Point and stare.

SUBSYSTEM: ISS

PRIMARY_POINTING: ISS_NAC to Enceladus (0.0,5.0,0.0 deg. offset)

REQUEST_ID: ISS_018EN_PLUMES001_PRIME

REQUEST_TITLE: ENCELADUS Geyser/Plume Search

REQ_DESCRIPTION: 1;ENCELADUS Geyser/Plume Search 1x1xNPp -- 3 different exposures

BEGIN_TIME: 2005 NOV 27 19:00:00 UTC

END_TIME: 2005 NOV 27 20:00:00 UTC


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edstrick
post Nov 30 2005, 06:24 AM
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Various comments and responses:
Looking at jmknapp's side-by-side posting of images from 144000 and 174000 km, there are quite strong differences in plume apperances. I really doubt that the plumes are "chugging"--varying rapidly with time over an hour or whatever, so I expect that the effect is parallax. Since multiple observation were taken over a moderate range of viewing azimuths, if the plumes were in fact time-invarient, it will be possible to do computed tomographic reconstructions of their 3-D structure. Not perfect, since it would be "limited angle tomography", but extremely useful.

Regarding flyby's optimized for gravity measurements, once the pole is in winter night, imagery will be relatively useless, unless the plumes continue to vent into sunlight well the shadowed surface. Thermal imaging would still be useful, but nighttime passes would be most useful to "divert" to gravity measurements. Gravity mapping from flyby's is best done with passes at different latitudes and different longitudes, so (besides searching for gravitational anomalies) they can measure the triaxial ellipsoid shape of the gravity field to compare with the triaxial ellipsoid shape of the surface, which tells you a *LOT* about concentration of mass toward the center: Core vs No-Core, etc. Magnetic data from such flybys also tells you about interactions with Saturn's mag field, which at Jupiter revealed electically conductive, presumably fluid, layers inside moons.

Regarding scattered light problems, while I'd seen fogging and some blotching beyond the limb of earlier moon images, I never saw anything that really looked plume-like, and never got pointed toward specific comparison images. What really pushed my buttons in the January images were that the features progressively increased in contrast, narrowed, and sharpened toward the limb, and there were no plumelike features at all on the terminator side of the overexposed and saturated crescent, just the usual trace of camera-fog.

Anyway, I'm not claiming credit.. that goes to the team, paricularly for a very nicely designed imaging sequence that covered all bases and seems to have provided far better information on the venting than can be extracted from the previous images. I'll be very interested in color results and phase angle dependent photometry. Does the December sequence go to higher phase angles?.. the graphic suggests it may..... the results might be even more spectacular if so.

jmknap: If the venting is from exposed ice, the hottest ice will "retreat" relative to colder ice. Everythign I see in the images of Enceladus suggests an extremely high thermal gradient below the surface. We can arm-wavingly-imagine venting pits retreating down into the surface, forming volcano-like or dry gyser-like pipes, with hot sublimating ice tens to hundreds of meters below the local surface.

Marz: The E-ring is very very faint, except at very high phase angles, where foreward scattering of sunlight by the fine dust-like ice grains makes it relatively bright. This scattering is probably mostly by diffraction or "Mie scattering" (which makes colorless and sometimes colored aureoles around the sun in our sky), and probably has only weak internally-scattered contributions that yield composition data. Certainly, there will be attempts as the mission proceds to get VIMS spectra of the plumes as close to the sources as possible. Cross fingers that they see anything beyond water ice.

I don't know the last decade's post-Voyager science on the E-ring, much less any of Cassini's beyond press release data. One model of the ring based on earthbased and Voyager photometry (and maybe polarimitry?) data stated that the ring had a narrow size range of particles and appeared to consist of more or less spherical water "droplets": flash frozen ice-sphere grains, rather than snow-like or crushed ice grains. This was one thing that suggested long before Cassini got there that Enceladus might actually be venting, rather than that we were seeing something like a torus of ejected ice from a recent impact or something.
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jmknapp
post Nov 30 2005, 01:24 PM
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QUOTE (edstrick @ Nov 30 2005, 02:24 AM)
Various comments and responses:
I really doubt that the plumes are "chugging"--varying rapidly with time over an hour or whatever, so I expect that the effect is parallax.  Since multiple observation were taken over a moderate range of viewing azimuths, if the plumes were in fact time-invarient, it will be possible to do computed tomographic reconstructions of their 3-D structure.  Not perfect, since it would be "limited angle tomography", but extremely useful.
*


Another complication would be that the solar phase angle is changing throughout, but maybe you're right that something could be done in that vein. FWIW, here's the position of the limb at 144,000 and 174,000 km out:



So that shows the range of angles involved. There were 19 NAC frames taken beween these extremes, at varying exposures.

Interesting that at 144,000 km the limb was nearly parallel and on top of the center scratch, and at 174,000 it cut across all three somewhat.


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Posts in this topic
- jmknapp   Enceladus Plume Search, Nov. 27   Nov 24 2005, 04:01 PM
- - jmknapp   Here's the view of Enceladus during the plume ...   Nov 26 2005, 11:02 PM
|- - ElkGroveDan   QUOTE (jmknapp @ Nov 26 2005, 11:02 PM)Here...   Nov 27 2005, 12:15 AM
||- - David   QUOTE (ElkGroveDan @ Nov 27 2005, 12:15 AM)Lo...   Nov 28 2005, 11:54 PM
|- - dilo   Thanks for all these informations, jmknapp (also i...   Nov 27 2005, 08:04 AM
|- - jmknapp   QUOTE (dilo @ Nov 27 2005, 04:04 AM)Really ho...   Nov 27 2005, 02:13 PM
|- - mgrodzki   that is a nice image… not color right? and i assum...   Nov 27 2005, 06:24 PM
|- - dilo   QUOTE (mgrodzki @ Nov 27 2005, 06:24 PM)that ...   Nov 28 2005, 06:41 AM
- - Decepticon   Images Up. http://saturn1.jpl.nasa.gov/multimed...   Nov 28 2005, 01:10 PM
|- - SFJCody   http://saturn1.jpl.nasa.gov/multimedia/ima...6/N00...   Nov 28 2005, 01:29 PM
- - alan   Possible plume? Doesn't look like a lens flare...   Nov 28 2005, 01:31 PM
|- - ugordan   QUOTE (alan @ Nov 28 2005, 03:31 PM)Possible ...   Nov 28 2005, 01:38 PM
|- - Bjorn Jonsson   This is the first time I see something like this t...   Nov 28 2005, 01:49 PM
|- - tedstryk   I am at work, or I would do this myself, but someo...   Nov 28 2005, 02:12 PM
|- - Bjorn Jonsson   QUOTE (tedstryk @ Nov 28 2005, 02:12 PM)I am ...   Nov 28 2005, 02:18 PM
- - Decepticon   Is there enough pics for a animation?   Nov 28 2005, 02:14 PM
- - Mariner9   ohmygod!!!!!!!!...   Nov 28 2005, 03:10 PM
- - Bill Harris   Whew. I'm not as up on the entire archive of ...   Nov 28 2005, 03:21 PM
|- - jmknapp   Too bad there isn't plume evidence on the dark...   Nov 28 2005, 03:27 PM
|- - ugordan   QUOTE (jmknapp @ Nov 28 2005, 05:27 PM)Too ba...   Nov 28 2005, 03:32 PM
||- - jmknapp   QUOTE (ugordan @ Nov 28 2005, 11:32 AM)Well, ...   Nov 28 2005, 03:44 PM
||- - ugordan   QUOTE (jmknapp @ Nov 28 2005, 05:44 PM)But an...   Nov 28 2005, 03:51 PM
||- - jmknapp   QUOTE (ugordan @ Nov 28 2005, 11:51 AM)Why do...   Nov 28 2005, 03:59 PM
||- - tedstryk   QUOTE (jmknapp @ Nov 28 2005, 03:59 PM)Not in...   Nov 28 2005, 04:49 PM
||- - jmknapp   Here's a map of the south polar region, based ...   Nov 28 2005, 05:56 PM
|||- - jmknapp   Found this image of the south polar region (approx...   Nov 28 2005, 06:41 PM
|||- - The Messenger   QUOTE (jmknapp @ Nov 28 2005, 10:56 AM)Here...   Nov 28 2005, 08:44 PM
||- - scalbers   QUOTE (tedstryk @ Nov 28 2005, 04:49 PM)I thi...   Nov 28 2005, 08:17 PM
||- - dilo   QUOTE (tedstryk @ Nov 28 2005, 04:49 PM)I thi...   Nov 28 2005, 09:03 PM
|- - JRehling   QUOTE (jmknapp @ Nov 28 2005, 07:27 AM)Too ba...   Nov 28 2005, 03:35 PM
- - tasp   What is the power source for this? {Wild speculat...   Nov 28 2005, 03:51 PM
- - Orlin Denkov   In the title of this thread isn't it Enceladus...   Nov 28 2005, 03:55 PM
- - volcanopele   ^^ Fixed   Nov 28 2005, 03:56 PM
|- - The Messenger   The source of the heat is truly perplexing. I hope...   Nov 28 2005, 04:48 PM
- - tasp   Maybe I am 'seeing' too much into your map...   Nov 28 2005, 06:29 PM
- - canis_minor   The features seen in these images are located at t...   Nov 28 2005, 07:21 PM
- - Bill Harris   The ridges and wrinkles in that region are a stron...   Nov 28 2005, 07:37 PM
|- - Bjorn Jonsson   I'm attaching a rendering I did showing the vi...   Nov 28 2005, 08:47 PM
|- - jmknapp   QUOTE (Bjorn Jonsson @ Nov 28 2005, 04:47 PM)...   Nov 28 2005, 10:01 PM
|- - mars loon   This news just released by CICLOPS website ...   Nov 28 2005, 10:31 PM
- - volcanopele   Special release for the Enceladus plume: http://c...   Nov 28 2005, 09:59 PM
|- - ugordan   QUOTE (volcanopele @ Nov 28 2005, 11:59 PM)Fo...   Nov 29 2005, 08:07 AM
- - Sunspot   What's also striking is how obvious the plumes...   Nov 28 2005, 10:48 PM
|- - mars loon   QUOTE (Sunspot @ Nov 28 2005, 10:48 PM)What...   Nov 28 2005, 11:29 PM
- - akuo   Looking at the raws I noticed that the whole backg...   Nov 28 2005, 11:29 PM
|- - EccentricAnomaly   The E-Ring is just such a donut of material around...   Nov 29 2005, 12:44 AM
- - edstrick   Regarding the plume images: Feb 20, I posted: htt...   Nov 29 2005, 07:50 AM
|- - volcanopele   QUOTE (edstrick @ Nov 29 2005, 12:50 AM)NOW.....   Nov 29 2005, 07:30 PM
|- - jmknapp   One thing that strikes me in the CICLOPS press rel...   Nov 29 2005, 08:08 PM
- - BruceMoomaw   Crowing about one's foresight is bad manners, ...   Nov 29 2005, 08:23 AM
- - edstrick   (grins a bit toothily at Bruce Moomaw, canary feat...   Nov 29 2005, 08:39 AM
- - Gsnorgathon   Good for you, Ed! Crow all you like! (Actu...   Nov 29 2005, 10:52 AM
- - edstrick   I doubt there's enough parallax during the hig...   Nov 29 2005, 11:55 AM
|- - ugordan   Regarding the possibility of more intense Enceladu...   Nov 29 2005, 12:16 PM
|- - jmknapp   We're set for a Christmas rerun: The above ...   Nov 29 2005, 02:18 PM
||- - ugordan   QUOTE (jmknapp @ Nov 29 2005, 03:18 PM)The ab...   Nov 29 2005, 02:33 PM
||- - jmknapp   QUOTE (ugordan @ Nov 29 2005, 10:33 AM)That...   Nov 29 2005, 03:40 PM
|- - The Messenger   QUOTE (ugordan @ Nov 29 2005, 05:16 AM)Option...   Nov 29 2005, 05:18 PM
|- - jmknapp   QUOTE (ugordan @ Nov 29 2005, 08:16 AM)Regard...   Nov 30 2005, 01:59 AM
- - Omega   Regarding possible artifact-- QUOTE Images of oth...   Nov 29 2005, 05:53 PM
- - scalbers   My guess is that the rays are actual streamers of ...   Nov 29 2005, 08:44 PM
|- - Rob Pinnegar   QUOTE (scalbers @ Nov 29 2005, 02:44 PM)My gu...   Nov 29 2005, 09:20 PM
|- - Marz   QUOTE (scalbers @ Nov 29 2005, 02:44 PM)Would...   Nov 29 2005, 09:20 PM
|- - JRehling   QUOTE (scalbers @ Nov 29 2005, 12:44 PM)My gu...   Nov 29 2005, 09:21 PM
|- - tedstryk   This makes me wonder about Europa, where high phas...   Nov 29 2005, 11:44 PM
- - BruceMoomaw   QUOTE (jmknapp @ Nov 29 2005, 08:08 PM)If it ...   Nov 30 2005, 03:00 AM
|- - tedstryk   Galileo came up cold, but Europa is much bigger, a...   Nov 30 2005, 03:54 AM
|- - The Messenger   QUOTE (BruceMoomaw @ Nov 29 2005, 08:00 PM).....   Nov 30 2005, 04:34 AM
- - edstrick   Various comments and responses: Looking at jmknap...   Nov 30 2005, 06:24 AM
|- - jmknapp   QUOTE (edstrick @ Nov 30 2005, 02:24 AM)Vario...   Nov 30 2005, 01:24 PM
||- - ugordan   QUOTE (jmknapp @ Nov 30 2005, 02:24 PM)Intere...   Nov 30 2005, 01:38 PM
||- - jmknapp   QUOTE (ugordan @ Nov 30 2005, 09:38 AM)Of cou...   Nov 30 2005, 04:48 PM
|- - The Messenger   QUOTE (edstrick @ Nov 29 2005, 11:24 PM)What ...   Dec 1 2005, 03:17 AM
- - edstrick   And, Oh... from the Utter Loonacy Department. M...   Nov 30 2005, 06:29 AM
- - Webscientist   Astonishing news, I'm really surprised to see ...   Nov 30 2005, 09:36 AM
- - Bill Harris   > from the Utter Loonacy Department... Aye, Ca...   Nov 30 2005, 10:42 AM
- - BruceMoomaw   That last quote was actually a misinterpretation b...   Dec 1 2005, 12:33 AM
|- - mars loon   QUOTE (BruceMoomaw @ Dec 1 2005, 12:33 AM)Wha...   Dec 1 2005, 12:48 AM
|- - ugordan   QUOTE (BruceMoomaw @ Dec 1 2005, 01:33 AM)Wha...   Dec 1 2005, 08:39 AM
|- - jmknapp   QUOTE (BruceMoomaw @ Nov 30 2005, 08:33 PM)Th...   Dec 1 2005, 12:23 PM
|- - jmknapp   Closeups of the tiger stripes are intriguing but a...   Dec 1 2005, 01:08 PM
- - deglr6328   There is a second derivative of two ammonia absorp...   Dec 1 2005, 09:14 AM
- - edstrick   Ugordan: "....but haven't there been some...   Dec 1 2005, 11:28 AM
- - dvandorn   Based on the shadows, the sun is on the *right*......   Dec 1 2005, 01:14 PM
|- - jmknapp   QUOTE (dvandorn @ Dec 1 2005, 09:14 AM)Based ...   Dec 1 2005, 01:22 PM
|- - ugordan   QUOTE (jmknapp @ Dec 1 2005, 02:22 PM)So the ...   Dec 1 2005, 02:04 PM
- - dvandorn   In the context image, your point is clear... but g...   Dec 1 2005, 02:18 PM
|- - jmknapp   QUOTE (dvandorn @ Dec 1 2005, 10:18 AM)In the...   Dec 1 2005, 02:40 PM
- - David   Enceladus is the "shiniest" moon in the ...   Dec 1 2005, 02:47 PM
|- - ugordan   QUOTE (David @ Dec 1 2005, 03:47 PM)Enceladus...   Dec 1 2005, 02:55 PM
- - Bill Harris   QUOTE (jmknapp @ Dec 1 2005, 08:40 AM)It...   Dec 1 2005, 04:09 PM
- - tasp   How fast are these plumes turning Enceladus inside...   Dec 1 2005, 05:01 PM
|- - ugordan   QUOTE (tasp @ Dec 1 2005, 06:01 PM)Any chance...   Dec 2 2005, 08:10 AM
- - dvandorn   The question that comes to my mind is: If "w...   Dec 2 2005, 08:14 AM
- - jmknapp   Interesting comments from Dr. Carolyn Porco: ...   Dec 2 2005, 11:18 AM
- - ugordan   QUOTE (jmknapp @ Dec 2 2005, 12:18 PM)Interes...   Dec 2 2005, 11:50 AM
- - jmknapp   QUOTE (ugordan @ Dec 2 2005, 07:50 AM)So they...   Dec 2 2005, 11:57 AM
- - ugordan   Regarding the source of the heat, there is a relat...   Dec 2 2005, 12:15 PM
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