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Enceladus Plume Search, Nov. 27
jmknapp
post Nov 28 2005, 02:45 PM
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Here's what I get using SPICE data and artificially illuminating the dark side:



The NAC image is rotated from that above (which is oriented with the north pole up), but the "plume" appears to be in about the center of the crescent, which would place it very near the south pole.

Another south pole hot spot?

Here's the corresponding raw image, rotated to about the same crescent orientation:



link to raw image


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Mariner9
post Nov 28 2005, 03:10 PM
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ohmygod!!!!!!!!!

I had no idea they were planning this. I checked the raw images this morning and I'm still pulling my jaw (metaphorically) off of the floor.

I'm rarely at a loss for words. This is no artifact, no lens trick, this is the real deal.
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Bill Harris
post Nov 28 2005, 03:21 PM
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Whew.

I'm not as up on the entire archive of Enceladus images as I should be, but do we have a set of earlier images of the south polar region?

--Bill


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jmknapp
post Nov 28 2005, 03:27 PM
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Too bad there isn't plume evidence on the dark limb though, rather than just where one might expect a "diamond ring" effect?


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ugordan
post Nov 28 2005, 03:30 PM
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QUOTE (jmknapp @ Nov 28 2005, 04:45 PM)
Here's what I get using SPICE data and artificially illuminating the dark side:

The NAC image is rotated from that above (which is oriented with the north pole up), but the "plume" appears to be in about the center of the crescent, which would place it very near the south pole.

Another south pole hot spot?

Here's the corresponding raw image, rotated to about the same crescent orientation:
*

I suppose it would really be an overkill, but I figure a precise way to match the viewing geometry would be extracting the S/C velocity vector relative to Enceladus from the kernels and comparing it with one of the long star trails visible in the background. It would probably be too much work, but might be interesting to see if it's doable.

Anyhow, even this is accurate enough to conclusively say the plumes (plural!) are coming from the vicinity of the south pole.

In my mind, there's not a tiniest bit of doubt whether the feature we're seeing is real. The nail in the coffin to the nay-sayers would probably be a WAC shot which, I predict would show the very same plumes. wink.gif


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ugordan
post Nov 28 2005, 03:32 PM
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QUOTE (jmknapp @ Nov 28 2005, 05:27 PM)
Too bad there isn't plume evidence on the dark limb though, rather than just where one might expect a "diamond ring" effect?
*

Well, if you consider the plume is not hot silicate lava but rather water wapor, I'd be in fact surprised to see it glow in the dark!


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JRehling
post Nov 28 2005, 03:35 PM
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QUOTE (jmknapp @ Nov 28 2005, 07:27 AM)
Too bad there isn't plume evidence on the dark limb though, rather than just where one might expect a "diamond ring" effect?
*


Yeah, it's enough to make a jury consider acquitting... but I think this is a clincher for anyone who doesn't want to pop the champagne prematurely: Instead of one flare due to a bright limb, there are three distinct ones, with darkening inbetween. If we were merely seeing supersaturated brightness bleeding out, why wouldn't it bleed in the areas between the plumes, too? After all, they have more bright limb near them than the two outer plumes do.

This is a done deal -- Enceladus is venting. Now the interesting questions are: What is the shape and volume of the reservoir that is providing the fireworks? What is the access from subsurface to surface? And can we drop a submarine in there?
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jmknapp
post Nov 28 2005, 03:44 PM
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QUOTE (ugordan @ Nov 28 2005, 11:32 AM)
Well, if you consider the plume is not hot silicate lava but rather water wapor, I'd be in fact surprised to see it glow in the dark!
*


But any vapor on the dark-limb side might only have to gain a little altitude before it was in sunlight?


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ugordan
post Nov 28 2005, 03:51 PM
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QUOTE (jmknapp @ Nov 28 2005, 05:44 PM)
But any vapor on the dark-limb side might only have to gain a little altitude before it was in sunlight?
*

Why do you insist on the plumes originating from the dark side? There isn't much evidence to support this. In any case, if it were on the dark side, when it rose to get into sunlight, it would probably appear to be practically in front of the sunlit crescent, due to the very high phase angle.

In the light of the recent discovery, I think we'll need to re-analyze the Feb 17 high phase, outbound observations. There was one suspicious cloud-looking thing above the south pole also present back then, but it was attributed to scattered light/overexposure.


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tasp
post Nov 28 2005, 03:51 PM
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What is the power source for this?

{Wild speculation alert}

There is a small asteroid, Toro, that was until about a 100 years ago, in a resonant orbit around the sun with Venus. Since then it has been in a resonance with earth.

IIRC, the transition period took several years.

Is there any feasability that Enceladus is doing something similar with other moons of Saturn? Could Enceladus have an orbit around Saturn that periodically swaps resonances with 2 other satellites? Perhaps the period 'overshoots' slowly one resonance and oscillates back towards another which it overshoots and repeats the process. We see the plumes as powered from the internal heating from the times the resonances are strong and flex the crust (like Io), but our observations are in a time period between and we don't calculate that Enceladus is currently in a resonance.

I don't have the math skills or theoretical background to evaluate this.

What other possibilities exist for heating Enceladus? Radionuclides seem most unlikely, residual heat from an impact would seem to be something that would dissipate very rapidly. Solar heating of an object with an albedo of 1 is ruled out.
Formation heat should have dissipated billions of years ago. Electrical effects of Saturn's magnetosphere are too weak (by orders of magnitutde).

What else is there to heat Enceladus?

We have visible plumes, what kind of dissipation are we looking at? Megawatts?

Great fun figuring this one out!
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Orlin Denkov
post Nov 28 2005, 03:55 PM
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In the title of this thread isn't it Enceladus that should be written tongue.gif
edit: oop, already correct, sorry smile.gif


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volcanopele
post Nov 28 2005, 03:56 PM
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^^ Fixed


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&@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io
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jmknapp
post Nov 28 2005, 03:59 PM
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QUOTE (ugordan @ Nov 28 2005, 11:51 AM)
Why do you insist on the plumes originating from the dark side?
*


Not insisting, I just said that it's too bad there isn't evidence elsewhere too, rather than just in the center of the crescent.

QUOTE (ugordan @ Nov 28 2005, 11:51 AM)
In the light of the recent discovery, I think we'll need to re-analyze the Feb 17 high phase, outbound observations. There was one suspicious cloud-looking thing above the south pole also present back then, but it was attributed to scattered light/overexposure.
*


Sure enough, and lo and behold that suspicious cloud-looking thing was very near the south pole too as you say, and not in the center of the crescent!



In that image north is oriented up.

Dismissed at the time as an artifact? Well, well!


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The Messenger
post Nov 28 2005, 04:48 PM
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The source of the heat is truly perplexing. I hope they will schedual some gravity runs of Enceladus in the extended mission. Enough to obtain a reasonable handle on mass distribution.
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tedstryk
post Nov 28 2005, 04:49 PM
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QUOTE (jmknapp @ Nov 28 2005, 03:59 PM)
Not insisting, I just said that it's too bad there isn't evidence elsewhere too, rather than just in the center of the crescent.
Sure enough, and lo and behold that suspicious cloud-looking thing was very near the south pole too as you say, and not in the center of the crescent!



In that image north is oriented up.

Dismissed at the time as an artifact? Well, well!
*

I think that there was always suspicion, but they wanted to avoid the humiliation of announcing a great discovery and then having to retract it.


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