Dione Image Products Options

[MarcF]

Thanks Graig. It was indeed in your earlier post regarding the CHARM presentation that I heard about the possibility of a dionean plume. But no other info about it anywhere else.

Concerning the crescent picture, I can also see a kind of "hazy feature" above the limb. But it's really difficult to conclude. Moreover, it's not apparent in the second picture (artefact or different viewing angle ?).
It would be so great to detect a current active Dione !!

Marc.

[ugordan]

That's definitely looking like a scattered light artifact. It appears right below the thickest and brightest part of the crescent. These are probably just optical navigation images, the phase angle isn't all that favorable for a plume search.

[dilo]

I have to agree with ugordan, following elaboration with negative/smoothed weak details show that there isn't any trace of extended plume "à la Enceladus".

Attached thumbnail(s)

 

[belleraphon1]

Thanks for the comments MarcF, ugordon, and dilo....

Have to "kinda" agree. Wondered if the other image was taken at a slightly different exposure setting.

The CHARM presentation says the mass loading at Dione is an order of magnitude below what is seen at Enceladus. So I picture that as, perhaps, diffuse shedding of internal gassy molecules. It may not show up as a distinct plume. It may be distributed along the fracture systems......

What was the geometry of the Dione 16 encounter? What longitudes did that cover at closest approach?

Craig

[dilo]

Another couple of false color elaborations based on a sequence of increasing exposures, clear filter images:


(start images: N00064540/41/42)
First one associate an RGB channel to each image while in the second one I tried to highlight dimmest details.
To highlight the small difference between position angle of subsolar point and the faint glow, which seems slightly rotated toward left (the difference is about 20 deg, measured from Dione center).
Again, not enough to say if there is a weak plume or an artifact but seems interesting...

[JRehling]

Another couple of false color elaborations based on a sequence of increasing exposures, clear filter images:


(start images: N00064540/41/42)
First one associate an RGB channel to each image while in the second one I tried to highlight dimmest details.
To highlight the small difference between position angle of subsolar point and the faint glow, which seems slightly rotated toward left (the difference is about 20 deg, measured from Dione center).
Again, not enough to say if there is a weak plume or an artifact but seems interesting...

Just as a skeptical hypothesis, I wonder if this cometlike halo could be due to the summation of light coming from Dione plus some generalized light leak placed to the right.

[Big_Gazza]

Some nice Dione images from Rev 27:

crescent stitch
http://www.members.optusnet.com.au/ics_gs/...4755_mosaic.JPG

night side

http://www.members.optusnet.com.au/ics_gs/...0064758_mod.JPG

[ugordan]

Just as a skeptical hypothesis, I wonder if this cometlike halo could be due to the summation of light coming from Dione plus some generalized light leak placed to the right.

That's probably about right. All Cassini images exhibit an ever-so-slight halo around bright objects. I don't know if it's an inherent "feature" of the narrow angle camera or residual haze traces or simply diffraction/PSF effects. Probably a bit of everything. In any case, if the Dionian hypothetical plumes are real and much weaker than Enceladean (as it's been suggested), about the only way to see them would be to occult the Sun so there's no illuminated crescent visible. No saturnshine would be a bonus, too. Even then, it's a question of the plumes themselves being in sunlight. That's a lot of geometry constraints.
AFAIK, this is not going to happen since Cassini already executed its dedicated Dione flyby and is left with only a couple of distant flybys in the primary mission. The chance of the geometry being such that Dione will occult the sun is miniscule. We're likely stuck with only hints of activity from the magnetometer readings.

[dilo]

I agree about the weak, estended halo similar to a cometary coma: probaly it is an artifact due to sensor + spurious light diffusion.
I was talking about the inner, "blue" (referred to 2nd image) halo within 1 Dione radius, which appear elongated and not exactly allineated to the Sun illumination... but, yes, I still in doubt about real interpretation and, yes, probably the only way to know is through unprogrammed eclipse...
What about magnetometer readings?

[dilo]

Also very last images of Dione limb are odd, with a glare not aligned with Sun direction...
http://saturn.jpl.nasa.gov/multimedia/imag...3/N00064895.jpg
I do not have photo-elaboration instruments in order to betteer see weak details but the fact they are still taking lot of images like this is a clear hint that they search/suspect something on Dione volcanism, IMO

[dilo]

Perhaps I have to step back on my last post... more careful analysis of entire sequence showed that, probably, glare is simply due to higher albedo in the left portion, as clear from this lower exposure:
http://saturn.jpl.nasa.gov/multimedia/imag...3/N00064886.jpg
anyway, they are still taking lot of images like this.

[ugordan]

the fact they are still taking lot of images like this is a clear hint that they search/suspect something on Dione volcanism, IMO

Well, it's not like they can choose NOT to take very high phase images right now

[MarcF]

Some new hints about a current Dione internal activity from the 38th annual division for planetary science meeting :

Oral session 72
abstract presentation 72.01, Gerald Schubert.
Interiors of Enceladus, Dione and Rhea
http://www.abstractsonline.com/viewer/view...2-AB52D1F706C5}
Marc.

[scalbers]

Thought I'd mention a Dione map update using one of the July, 2006 images (as suggested in another thread). The URL for my latest map is:

http://laps.noaa.gov/albers/sos/sos.html#DIONE

[MarcF]

A little reminder of the Voyager 1 Dione flyby, a long time ago:

http://saturn.jpl.nasa.gov/multimedia/imag...fm?imageID=2333

Marc.