nprev: "The whole reason I'm pushing the flux tube idea and other external systemic effects as putative (and probably synergistic) causes for the observed geological activity is that I find it difficult to accept a significant degree of internally asymmetric mass distribution for Enceladus. ...."

A weak flux tube with low current will also provide weak heating of Enceladus. There's also questions of how current would penetrate couples through the surface to the presumably conductive interior. I recall discussions of that in reference to Io, and I think I recall discussions of searching for nighttime glows on Io where flux tube current passes through conductive spots triggering possible auroral or arcing emissions. What they found or concluded I don't remember.

How much or little flux tube is possible comes out of quantitative comparisons of models of atmosphere and plume neutral and ionized gas interactions with Saturn's magnetic field, and the observations along flyby trajectories by Cassini. I'm not about to guess, but at a purely arm-waving-arguement level, the interaction seems to point to the plume and it's volume in space dominating the interaction.

Right now, the expectations are that Enceladus is pretty fully differentiated and any "rock"... more likely rock-mud core (at least at it's surface interface with the mantle) should be pretty fully relaxed and pretty level with the local gravitional potential. But the question remains why is the activity most at the south pole, and generally least at the north pole. Very very odd. My best weak guess is a single-cell convection pattern in the mantle ice, resulting in sinking under a stable crust in the north and upwelling in the south. But that might make features more like the coronae on Miranda. Our biggest hope for understanding this if we don't detect a flux tube (and that should equally heat the north and south in the simplest models), is gravity measurements on the internal mass distribution to make tidal heating models less-unconstrained.

One prediction which is becoming fairly consistent in planetary geology is that small worlds are likely to develop single-cell mantle convection cycles, which could also explain the asymmetry between the Moon's and Mars' two hemispheres (plus the Tharsis Bulge). In the case of Enceladus, one thing that intrigues me is the "patchiness" of its resurfacing -- which seems to me to imply that Enceladus has undergone a limited number of heating episodes during the Solar System's history, with its spin axis wandering between such episodes. This, of course, is what you might expect from a history of complex tidal interactions between Enceladus and the other moons.

One thing that seems clear is that during "heatups", some areas get totally resurfaced, while other areas have very soft mobile ice only a few kilometers under a really cold brittle crust that relaxes and develop those spectacular crazing and cracking patterns beautifully shown in the pic posted a page or two back. The control of the cracking by the topography to my mind suggests that convex surfaces like crater rims were colder and stayed cold enough to be stiff to greater depth than concave surfaces on crater floors etc. This should be very amenable to quantative modeling to produce the same geometry fracture pattern.

What's particularly significant, though, is that areas like these had soft ice under the brittle crust that was *NOT* convecting or flowing so as to horizontally deform the brittle crust with tectonic processes. It's a pretty pure relaxation-only process. So some soft ice was mobile, probably convection, some was not.

Go Figure. Sustained geological analysis will help unravel the relative sequence of events, first on local, then on global scales. Absolute times and durations we won't know, or only guess at.

Here's an animation of the Christmas flyby:

Enceladus Dec. 25, 2005 flyby, outbound (1.7MB AVI)

According to pointing info in the SPICE kernels, the only ORS observations are slated to occur briefly during the inbound, low-phase leg. But Jason has indicated that this is perhaps under review. I don't know what the tradeoffs are, but it seems a shame to pass up the opportunity to do more observations of the plumes, maybe over a greater range of time as the moon rotates outbound.

jmknapp: Seriously, you should think about writing a (short) paper on your sim. I don't know if others did similar simulations, but the results are intriguing. Perhaps with a little bit of playing around with distributions of venting locations you could make an even better fit to the albedo map. The paper doesn't have to be a hundred pages long, a few pages might do, describing your reasoning, steps and discussing your tentative results a bit.

Someone's bound to do this anyway and you might feel bad when they take the credit for it.

If Joe is interested in that, the Lunar and Planetary Science Conference would be a good way to go. They publish two-page "abstracts," and their deadline is January 3. --However, if he does want to publish anything, of course, that is really "doing science" which means he would have to strictly avoid even giving the impression that he has looked at any Cassini Enceladus data that has not been delivered to the PDS. That would be a no-no at this point! I think the early Enceladus data should be part of the next PDS release, right? And I hear there is a publication coming up, perhaps in Science, perhaps in January, which should free other scientists' tounges a bit...

--Emily

Yeah, I seem to recall something about that in the MER documents, something like any early released information is not to be published for a set time? Of course, "published" may be a nebulous concept, what with web-publishing and all. I suppose it means not in peer-reviewed venues? Or perhaps, strictly, anywhere?

Yeah, now that preliminary versions of "data" are available on the Web for the rovers and Cassini it's much harder for people on science teams to police access to data. Obviously scientists who are not on the imaging teams for either mission look at the pictures and take note of things that they eventually want to publish about. But they absolutely cannot publish scientific analysis of anything that is out there -- raw images, press released images, whatever -- until the data is formally released to the community via the PDS. In the past, when people have published about press released images, they have been "drummed out of the business" (in the words of one scientist I talked with recently). Once it's in the PDS though, it's fair game. This is to give the scientists who've worked to bring the instruments to space a first chance to publish about the data, and also to calibrate the data properly based on their unique knowledge of the instruments before it's made available to scientists who don't have that unique knowledge and experience.

--Emily

Before anyone who is not familiar with the practices gets scared, I think a bit of clarification is in order. Since there are no formal rules in place preventing anyone from publishing results based on publicly-released data, then stating that someone "absolutely cannot publish scientific analysis of anything that is out there...until the data is formally released to the community via the PDS" is, forgive me, a bit of hyperbole.

Of course, as you noted in the portion of your post that I elided, scientists risk condemnation from colleagues (viz., "drummed out of the business") for "claim jumping" or even outright rejection by a publisher. However, no one can be prevented from submitting something for publication based on data, in whatever form and however unreliable, that is in the public domain, regardless of whether it has been formally validated and placed on one of the PDS Nodes. Period. I may be mistaken but my understanding of NASA's current (and recent) policy regarding data is that all data are in the public domain, and while the data acquirers have a brief period of time for validation, usually six months, they have absolutely no proprietary rights.

Now Cassini may have been grandfathered in under the "old" system (e.g., Voyager-era where some teams did have proprietary rights) but I'd have to check the specific policy. However, I'm pretty sure MER operates under the current rules that others missions (e.g., Discovery, MGS, Mars Odyssey, etc.) fall under.

Having said all that, I would never trust a paper based on data that have not been validated. And I have a hard time believing that any respectable peer-reviewed journal would even consider, let alone accept, any such submission. Nevertheless, there is absolutely nothing to prevent someone from trying.

This post has been edited by AlexBlackwell: Dec 15 2005, 09:40 PM

In the specific case that was being discussed here, the mathematical modelling is perfectly legitimate for publication, assuming it was done correctly. And it would be quite reasonable to add to it a note about making a formal comparison with Cassini images when they become available, "but a preliminary examination of unvalidated data suggests...".

Phil

How about this though--it's based on the locations of the tiger stripes, the existence and nature of which was not known previously--the locations determined from un-PDS'ed "raw" images from the ISS team. So would that then make any results tainted?

As for correctness--you are right--a little more verification is called for.

In this case, I think jmknapp is stepping around their toes, but not on them. His approach is original and well conceived. Give the devil his due.

THE SYSTEM makes the assumption that the PI's are in the best position to validate and evaluate their own data. Most of the time this should work well, but on several of the current missions I have serious doubts.

For example, the WMAP team has been camped on the 2d & 3rd year data for 2-3 years. Literally hundreds of papers have been written that are based on first-year results, and some of these present serious challenges to the initial WMAP team findings.

So why the silence? Serious challenges have been raised, and I am of the opinion the WMAP team members are sitting on data they are either unwilling or unable to defend. As long as this stalemate continues, how can the science progress?

All I'm really saying is that I'd rather be on a ship to another planet at the moment that a certain team leader discovers any of the raw Cassini data being published in any form of scientific analysis by anybody not on the team.

That being said, here's an example of a paper recently presented at AGU by a scientist who spoke generally about the geophysical effects of a modeled plume on "mini-moons" including Miranda, Enceladus, Mimas, and Proteus. It's a nice example of not talking about the gorilla in the room.

--Emily

I reckon that's still not playing by the rules.

I'd suggest that the best way to approach this would be to wait for the first publication(s) on the tiger stripes to appear. Once a paper has been published that maps the relevant features' positions and discusses their nature, then, as long as you properly cite that paper as the basis for your model, I would think that it would be OK.

Of course, you still wouldn't be able to include in the paper actual Cassini data until they're on the PDS, but for the purposes of your simulation, the images themselves are probably not necessary, as long as the sources' likely positions have already been provided elsewhere. I guess the comparison albedo map could be based on Voyager data or any relevant publications that contain such a Voyager data-based map.

One thing that's almost as bad as publishing work based on data that's still proprietary (at least when it's not yours! ) is to knowingly publish work based on that of others while not citing the original authors' paper. The instrument science teams quite rightly expect and deserve credit for these initial discoveries, as without their instruments, the data wouldn't be available in the first place, and overall (I know there are exceptions), I think that this way of doing things is pretty fair to all.

Finally, the other thing you could do is to contact the relevant science team suggesting a collaboration, offering coauthorship to them. You may be pleasantly surprised.

What "rules"? And how are these rules to be enforced? And by who?


Please show me a reference that the data in this case (especially raw, unvalidated data publicly released on the Internet) are proprietary.