[X] My Assistant

[MarcF]

By making order in some of my old documents about the Voyager 2 mission, I got a look on the 20 years old Miranda pictures and I realized how similar Miranda and Enceladus really are.
http://photojournal.jpl.nasa.gov/jpeg/PIA01490.jpg

Both have about the same size, the same density (same composition ?). And the surfaces are amazingly similar too (even if Miranda's one seems in general older). Both might be in resonance with another moon, Ariel and Dione respectively (we could even expand the similarities to these two moons).
Miranda and Enceladus surfaces comprise corona-like structures surounded by older cratered terrains. In both cases, one is exactly localized at the south pole (self-rolling to place this area of low density at the south pole is suspected in both cases).
The most striking similar features seem to be Elsinor corona on Miranda and the corona-like structure on Enceladus localized between about 120 and 150 west.
These two worlds may share a common geological story. The origin of the Miranda features is still not really understood nowadays. So the current studies of Enceladus might also help to better understand Miranda (and vice versa).
Does someone know if serious comparative studies exist (or are on the way) ? I did not find any yet.
Marc.

[Rob Pinnegar]

It's hard to imagine that this *wouldn't* be a study topic eventually, although whether or not anyone's working on it right now is a tough call.

Guess it depends on how many other interesting topics there are out there, and how many people are avaliable to work on them. Voyager-related stuff was still being published in journal articles well into the 1990s at least... so someone will get to it sooner or later.

[elakdawalla]

There's some people working on this very actively right now, Francis Nimmo and Bob Pappalardo (aka vexgizmo).

Large Icy Diapirs and Small Icy Satellites: Reorientation of Mini-Moons

And I think it's mentioned in the recent Nature paper too:
Diapir-induced reorientation of Saturn's moon Enceladus

Also I'd be shocked and amazed if Paul Schenk hasn't been putting some thought into this...

--Emily

[MarcF]

Thanks a lot Emily.
Really interesting.
I think that comparative studies of such similar worlds will really bring a lot of interesting results.
I'm happy to see that it's indeed on the way.
Marc.

[Rob Pinnegar]

I just went back and took a quick look at some of the Voyager 2 shots of Miranda, looking for similarities to Enceladus (as per the topic of this thread).

One thing that is really noticeable about Miranda is that many of its craters exhibit the same kind of "fuzzy" appearance that we see on Enceladus. I suppose that we can be fairly certain, in Enceladus' case, that this is the result of several billion years of deposition of frost from the plumes.

That sort of begs the question as to whether we can use crater "fuzziness" to determine, from the Voyager images, whether Miranda still has intermittently active plumes. Since neither of the two recently discovered outer rings of Uranus share Miranda's orbit, it wouldn't appear that it is active at the moment. However, if it was active, say, ten million years ago, that would provide some pretty strong evidence that its activity is only dormant rather than extinct.

[MarcF]

I indeed forgot to mention this other important similarity between the two moons.
I totally agree with you Rob, the older "Regios" seem to be covered with a thick layer (dust/snow ?)
Does someone have an idea about how long it would take to the E ring to disappear after interruption of Enceladus geyser activity ?

Marc.

[tasp]

The sphereicity of Miranda and Enceladus are quite different. To me it suggests vastly different interior stucture, Enceladus being liquidy up to quite close to the surface, and Miranda being cold and rigid to great depths.

{not to rule out amorphous affects of icy materials under stress at Miranda}