Enceladus Jet Sources Options

[Ron Hobbs]

I am right there with you, Craig. Actually, I am dreaming of high-tech gondolas carrying tourists among the caverns. Of course, a hydrobot/cryobot would do just fine. If these things do exist, they will be among the most wondrous environments discovered by the scientific imagination.

I wonder if Cassini's radar could try to catch a reflection off the pools?

[Stu]

Geyser-related story up on the BBC Sci Tech web page today: http://news.bbc.co.uk/1/hi/sci/tech/8495663.stm

[2552]

Another story from space.com: http://www.space.com/scienceastronomy/ence...ter-100209.html

ADMIN EDIT: Exobiology comments deleted per section 1.3 of the Forum Rules. Please take a moment to review them again.

Edit: My apology for not reading the rules the first time, won't happen again.

[alan]

Pardon the blast from the past. Anyone remember the leopard spots seen along some of the groves imaged during the earlier flybys?

http://www.ciclops.org/view_media.php?id=4783

Could they be related to the jets, perhaps being the sources of jets in the distant past when they emerged from a different part of the moon?

[volcanopele]

I doubt it. I suspect they are more related to the rough topography, outcrops or boulders, than with cryovolcanism.

[ugordan]

I suppose this is a good place to post this... I just finished up a color version of this observation and it turned out to have two bonuses to it I wasn't aware of. One is that Enceladus' shadow on the E-ring is faintly visible, a rare sight. The second one is the reason why I'm posting this. There's what looks like a dome above the plumes. If you look real closely at the (contrast-enhanced) image below you can pick it up as a discrete change in plume brightness gradient about 1 Enceladus radius above the south pole.



My initial reaction was that this had to be some kind of artifact, but now I'm not so sure. It's visible in at least 3 clear filter frames and a red and blue frame. Moreover, the position of Enceladus was different in the color frames and the feature still follows it, suggesting it's not an optics scattered light effect from Saturn or something (Cassini was in eclipse at that point IIRC, anyway). Here's a natural-ish color R+B image and a heavy unsharp enhancement.



It looks like a bow shock in the plume but my gut says the whole thing is too diffuse for that. What do you think? Artifact or real?

[nprev]

Hmm. Subtle, good catch!

To me, the 'dome' looks like it's produced by plume particles that are in the foreground of the general E-ring glow. In other words, I see Enceladus's circular black shadow on the E-ring in the background, and it looks like this is a perspective effect. Is there any way to make a stereo pair? That might be a good test of this idea.

[alan]

The dome appears to continue through the shadow and may wrap all the way around, perhaps its an optical effect of the e-ring related to the lighting

Light reflected off Saturn is illuminating the surface of the moon while the sun, almost directly behind Enceladus, is backlighting the plumes.

Below is your image with the histogram equalized.

[ugordan]

I can't see how it would be a lighting effect on the ring unless the sun happened to be precisely behind Enceladus. The phase angle was high, 174 degrees, but even that is still 17 NAC FOVs away from the sun!

It does seem to fit inside Enceladus' Hill sphere and is elongated in the N-S direction, though.

[alan]

Yea, thought about that after I hit post.

[nprev]

Ahh...my bad, Gordan, misinterpreted what you meant by 'dome'. Just to be sure I'm on the same page now, would characterize what I think you mean as a halo or even aureole that completely encircles the moon(?)

EDIT: Wow. Does indeed look like there's an enrichment of material in what appears to be Enceladus' Hill sphere. The N/S elongation might be due to the effects of Saturn's magnetic field on what (I guess) highly diffused water vapor mixed with OH & H3O radicals. Again, wow!!!

[remcook]

Yet another great spot, Gordan! And a beautiful image!

Elliptical halo caused by scattering by the ring particles of light coming from Enceladus? http://www.atoptics.co.uk/fz409.htm
Whatever it is, it's pretty cool.

[ugordan]

The N/S elongation might be due to the effects of Saturn's magnetic field

I wonder if it's merely the effect of particles being more stably bound to Enceladus in those directions than in the orbital plane. If it's linked to the Hill sphere at all, that is.

[ugordan]

Elliptical halo caused by scattering by the ring particles of light coming from Enceladus?

The problem with that is that this halo would be very very small. Remember the narrow-angle camera has a FOV of 0.35 so any ice halos we're familiar with here on Earth couldn't possibly completely fit into the frame. Not even in the wide angle camera.

I'll have to check if anything of the sort is visible in earlier observations, although they were nowhere as close to such a high phase angle.

[remcook]

Yeah, I don't know what angles these inner rings of these halos go to.

About the Hill sphere thing: would you expect the most material to be at the outer edge?