Rev 61 Enceladus (March 12 2008) Options

[ugordan]

The flyby blog appears to be down as well...

[brellis]

The JPL website must be getting hammered...I'm having a hard time getting in to the raw images. Wish I could grab them and set up a mirror somehow...

--Emily

I've decided to keep away from the NASA site, and just wait until somebody smart from UMSF has had a look at them.

[Stu]

I haven't been able to get a look at the raws since I came home from work, 3 hours ago...

Still, shouldn't complain, I guess; it's a sign that this fly-by has got a LOT of people out there intetrested in space exploration. We can't have it both ways!

Thanks to everyone who's posted images here. I'd have seen NOTHING otherwise!

[Stu]

Some quick "Hmmmm...."s... looking at um3k's excellent image...

1. What happened to the rest of these craters?
2. Ooh look, a "chevron" like on Miranda...!
3. Weird... re-frozen cryo-volcanoes..?

[Bjorn Jonsson]

The JPL website must be getting hammered...I'm having a hard time getting in to the raw images. Wish I could grab them and set up a mirror somehow...

I've seen only a single image so far. It's extremely slow with frequent errors. UMSF is extremely slow today as well (even slower than yesterday). I'm not sure I'll be able to post this message without errors ;-).

[stevesliva]

I find the TryAgain firefox plugin helps when sites are getting bombed:
https://addons.mozilla.org/en-US/firefox/addon/2462

Of course, that means I'm exacerbating the issue more than my share. But I'm selfish.

[marsbug]

Weird... re-frozen cryo-volcanoes..?

The crater to the upper left of the two marked seems to have something similar. It'll be interesting to see how many craters have this effect, and if its in anyway related to size.The image that pops into my head is a large impact producing a temporary lake of liquid water underneath it, which powers cryovolcanism.

[ugordan]

If I'm not mistaken, those two craters were apparent back in the Voyager imagery and led to various explanations like viscous relaxation of ice which (unlike other icy sats) seemed to be warmer and thus less rigid. Very few, if any of the craters on Enceladus have your typical crater-bowl-look seen on other worlds.

[Juramike]

The crater to the upper left of the two marked seems to have something similar. It'll be interesting to see how many craters have this effect, and if its in anyway related to size.The image that pops into my head is a large impact producing a temporary lake of liquid water underneath it, which powers cryovolcanism.

Or it punches through to a liquid layer and the open throat is the source for upwelling.

Just like the Evil eye of W Quivira or Coats Facula on Titan?

I can't wait to measure the ratio of inner diameter vs. rim diameter. It looks pretty similar.

-Mike

[mgrodzki]

wow… everything is real tied up. i guess nobody here has anything else from other sources?

[mgrodzki]

anyone find out if these dots are all “hot pixels” or otherwise?

Attached thumbnail(s)

 

[elakdawalla]

Gordan is right. Those distinctive Enceladan craters with up-domed floors, where the domes are heavily fractured, are very easy to explain through the process of "viscous relaxation," where the crater looked normal (bowl shaped or whatever) when it formed, but over time, and with help from heat conducting from the interior, gravity causes the ice in the crater to flow (in the solid state -- no volcanism or anything required here) to equalize the gravitational potential. Short-wavelength features take longer to relax because the strength of the ice comes in to play, so you get the most deformation acting on the longest wavelength, which is the up-down-up of the crater rim-floor-rim. As the floor domes upward, there are extensional stresses along the top of the dome, so it fractures. This is basically the same kind of stress regime that is being proposed to explain the "spider" feature in the center of Caloris as seen by MESSENGER on Mercury.

I looked around for some papers on viscous relaxation on Enceladus and this is what I came up with that's in the public domain.
http://www.lpi.usra.edu/meetings/icysat2007/pdf/6051.pdf
http://www.lpi.usra.edu/meetings/lpsc2007/pdf/2237.pdf

Mgrodzki, as ugordan pointed out here, those are stars. It's a long exposure becuase of the eclipse.

--Emily

[mgrodzki]

anyone find out if these dots are all “hot pixels” or otherwise?

ah… i just saw emily’s post. its super-exposed from rings shine, saturn shine… etc. so those could very well be stars picked up by the sensitive exposure.

[Juramike]

I took um3k's image (Stu's annotation added) and zoomed in on "3":





Side by side comparison with the T25 RADAR image of the "Evil eye" W Quivira feature on Titan (annotated and unannotated versions). The ratio of inner bulge and outer rim diameter are real close, even though "Evil eye" feature on Titan is ca. 5x bigger.

The central domes look larger and a little bit rougher ("bulgier?") than normal. Topography would help illuminate this (that's a stretch for a "shape from shading" pun). Maybe these are central dome craters where the rebound just didn't know when to stop?

-Mike

[EDIT: Just saw Emily's post. Fracturing would make the central domes look rougher. Might also explain the Evil eye of Titan if it is indeed a fractured-up central dome crater.]

[elakdawalla]

Since these places have names, we might as well be using them. Stu's "3" is Aladdin. The adjacent, more angular-outlined one is Ali Baba. Here's the Voyager view:



--Emily