[X] My Assistant

[jmknapp]

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

[Bill Harris]

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

[jmknapp]

Too bad there isn't plume evidence on the dark limb though, rather than just where one might expect a "diamond ring" effect?

[ugordan]

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!

[jmknapp]

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?

[ugordan]

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.

[jmknapp]

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.

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!

[tedstryk]

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.

[jmknapp]

Here's a map of the south polar region, based on Steve Alber's latest cylindrical projection (click for larger image):



This is an orthonormal projection, so the limb is the equator and the south pole ("tiger scratch" feature) is at the center of the image.