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Procyan
2008-Nov-02, 05:51 PM
Sometimes I see topography that looks like rivulets cut into the ice:

http://ciclops.org/view_media/26008/Enceladus_Rev_91_Flyby_-_Skeet_Shoot_8

Looking at the top central and left part.

Any ideas how these could be formed?

01101001
2008-Nov-02, 06:13 PM
Sometimes I see topography that looks like rivulets cut into the ice: [...]

I don't see the tributary structure that low-viscosity liquid flow would create. There are hints of branching, but I think that's just cracks that formed in sequence over time.

To my untrained eyes it looks more like flowing high-viscosity ice than water -- like the surface of a (much-colder-than-Earth) glacier, not a river system.

Procyan
2008-Nov-02, 06:31 PM
Yep, that would make sense. The ice fractures into dendritic pattern as it spreads out. Thanks

tusenfem
2008-Nov-03, 08:16 AM
Damascus Suclus, as well as all other 8 (?) are "stretch marks" of Enceladus, created by tidal flexing. Depending on where Enceladus is located,these are open (emitting water from below the surface) or closed, and all help creating the water plume that is observed in the southern hemisphere.

Here is a paper (http://www.agu.org/pubs/crossref/2008/2008GL035811.shtml) by Saur et al. where these Suclae (??) are discussed with respect to the magnetic signature. This is the way I can get to the original paper by Hurford et al. in Nature (http://www.nature.com/nature/journal/v447/n7142/abs/nature05821.html)

Don't know if this helps.

Procyan
2008-Nov-03, 10:12 AM
Thanks for the ref's. The sulci are fantastic features. Have you ever heard of jets on Europa? I wonder if tidal forces there drive jets or geysers, although I've never read of it happening. When I get rich I'll fund a Phoenix-style mission to study those. Maybe I could take out a loan :liar:

My original question was not clear. I was not referring to sulcus or large fissures, rather the finer structures that, to my eye, looked like complex patterns of erosion. I was wondering if Encedalus occasionally undergoes periodic heating sufficient to form a temporary atmosphere and/or ammonia slush on the surface. But tidal flex and possible solid state movements seem likely. The more or less parallel fine angular fractures, not fractal like stream beds.

tusenfem
2008-Nov-03, 11:02 AM
Thanks for the ref's. The sulci are fantastic features. Have you ever heard of jets on Europa? I wonder if tidal forces there drive jets or geysers, although I've never read of it happening. When I get rich I'll fund a Phoenix-style mission to study those. Maybe I could take out a loan :liar:


Nope, no jets at Europa, as far as I know, although there is cryo-vulcanism there. Europa does have "crack marks" on its surface that are cyloidal, and which are created by tidal flexing. of the surface. I think because of the moon-wide ocean under the icy surface there are no pockets like at Enceladus, that can be pressurized and cause jets.

More info will be obtained when we get the Laplace mission going. In January there will be a decision whether Laplace (2 or 3 sats to Jupiter) or Tandem (2 sats to Saturn) will get the go-ahead for the next step in the competition. If we get Laplace I will send you my bank account number so you can donate :-)



My original question was not clear. I was not referring to sulcus or large fissures, rather the finer structures that, to my eye, looked like complex patterns of erosion. I was wondering if Encedalus occasionally undergoes periodic heating sufficient to form a temporary atmosphere and/or ammonia slush on the surface. But tidal flex and possible solid state movements seem likely. The more or less parallel fine angular fractures, not fractal like stream beds.

I have not seen any mention of an atmosphere at Enceladus. I know from Joachim Saur that e.g. the "northern hemisphere" can easily be taken as zero density in his modelling of the magnetic interaction.

Oops, but a quick look at ADS corrects me, e.g. Tokar et al. (http://esoads.eso.org/abs/2006Sci...311.1409T) write in Science that:



The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 1027 H2O molecules per second) is inferred.


And there is a paper by Wannawichian et al. (http://esoads.eso.org/abs/2008JGRA..11307217W) also talking about an atmosphere in a JGR paper. I know the two co-authors and they are good scientists. But there is no quantitative mention of Enceladus's atmosphere, unfortunately.

Procyan
2008-Nov-03, 12:46 PM
Fantastic! I've got to read up on this. The Wannawickian abstract states:

Enceladus' mass loading region may be comparable in extent to Io's, whose auroral footprint emissions are clearly detected.

So is there a parallel with Jupiter's decametric radiations that are correlated to Io's orbit? Does the Saturn/Encedalus pairing cause something similar? I'm wondering if amateurs can detect using RadioJove type antennas?

Oh right, regarding your bank account, remember that optimism thing you say.