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Europa PR, A couple of new posts to the Photojournal
ngunn
post Nov 16 2011, 07:49 PM
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QUOTE (Paolo @ Nov 16 2011, 07:14 PM) *
the lucky few


I'm not one of the few, but I have now just skimmed through the paper's (freely available) supplementary material and having a personal fascination with subglacial hydrology I found it most interesting and informative. Thanks for the link. smile.gif
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stevesliva
post Nov 16 2011, 08:31 PM
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Again reminds me of sandstone over salt domes. The salt is deformable and causes some interesting chaos in the stone.
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stevesliva
post Nov 17 2011, 01:22 AM
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Article at NASA here links to larger versions of the Nature figures at UT:
http://science.nasa.gov/science-news/scien...1/16nov_europa/
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antipode
post Nov 18 2011, 02:55 AM
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Okay, I have a question (it may be dealt with in the paper, I don't know)

I assume this mechanism can explain the dark staining of the chaos regions, but what about the dark staining of many of the long cycloid cracks? Doesn't this assume that there HAS been a connection between the (presumably) deep ocean and the surface at some stage in the fairly recent geological past? One that doesn't need the upwelling mantle plume/subsurface lake mechanism to communicate with the surface?

Could there be regions of deep AND shallow ice? Can Jupiter's tides crack those errr cracks all the way to their ocean bases, or is there another mechanism that could bring those stains (are they tholins?) to the surface?

P
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elakdawalla
post Nov 18 2011, 02:57 AM
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They don't mention cycloids at all in the paper -- it's a modeling paper that only deals with chaos. So the paper doesn't address that at all. I'm curious to know the answer too!


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Juramike
post Nov 18 2011, 02:58 AM
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(Don't think they are tholins, more likely salts or other stains from water-soluble materials)


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antipode
post Nov 18 2011, 04:00 AM
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QUOTE (Juramike @ Nov 18 2011, 01:28 PM) *
(Don't think they are tholins, more likely salts or other stains from water-soluble materials)


Ah yes thanks mike, that would make a lot more sense. Where would the tholins come from?

P
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Explorer1
post Nov 18 2011, 07:05 AM
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Just a quick related question; how much do we know about Europa's rocky core and whether it is uneven in depth? I.e could there be places that it makes direct contact with the ice shell, without intervening water? Would an orbiter have to map it or could there be surface signs of these areas?
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Juramike
post Nov 18 2011, 12:03 PM
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QUOTE (antipode @ Nov 17 2011, 11:00 PM) *
Where would the tholins come from?


Tholins form from irradiation and zapping of mixes of methane and nitrogen. If tholins are forming on Europa, it would be from zapping of small organics encapsulated in the ices as clathrates. I'm not saying it's not possible that the stains are organic molecules, but my first suspect would be salts from below.

EDIT: yup, the dark stuff is consistent with hydrated sulfuric acid.

See:
Shirley et al. EPSC 2011, 6, (freely availalbe): http://meetingorganizer.copernicus.org/EPS...PS2011-1201.pdf

and (pay for article, abstract here): Orlando et al., Icarus 177 (2005) 528-533. http://www.sciencedirect.com/science/artic...019103505001983


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Gsnorgathon
post Nov 18 2011, 03:26 PM
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QUOTE (Explorer1 @ Nov 17 2011, 11:05 PM) *
Just a quick related question; how much do we know about Europa's rocky core and whether it is uneven in depth? I.e could there be places that it makes direct contact with the ice shell, without intervening water? Would an orbiter have to map it or could there be surface signs of these areas?

Short answer, no.

Given that the estimates for the depth of Europa's ocean are about 100km, it's extremely unlikely that the rocky crust would come anywhere near the ice shell. Total relief on the moon (Earth's moon, Luna) is about 22-23km IIRC, and the moon's got a much stiffer and thicker crust since it's so cold. Since Europa's geologically active, I'd expect it to have a warmer and softer crust that wouldn't be able to support as much relief. I'd guess the highest point on the crust is ~90km below the surface of the ice.
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eoincampbell
post Nov 18 2011, 03:38 PM
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QUOTE (Gsnorgathon @ Nov 18 2011, 08:26 AM) *
... it's extremely unlikely that the rocky crust would come anywhere near the ice shell...


But how are the purported "shallow lakes" forming in the first place?


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Phil Stooke
post Nov 18 2011, 03:46 PM
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"But how are the purported "shallow lakes" forming in the first place?"

Read this for an answer:

http://www.skyandtelescope.com/news/Subsur...-134059133.html


There have also been suggestions that the chaos areas form over deep hot water plumes in the ocean, which in turn form over ocean floor volcanic eruptions, but modelling might not allow that. I haven't seen it tested.

Phil



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Floyd
post Nov 29 2011, 10:16 PM
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The Nature article is quite nice (I'm one of the lucky subscribers). Is there a chance that some of the chaos terrain on Enceladus results from the same mechanism?


floyd
contact fdewhirst at forsyth dot org


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Phil Stooke
post Nov 29 2011, 11:06 PM
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There is nothing comparable on Enceladus. Totally different geology. There might be areas you could call chaotic if you wanted to but they are very different.

Phil


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MarcF
post Mar 9 2013, 04:02 PM
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Some new stuff from Europa:
"Based on new data from the W. M. Keck Observatory about Jupiter's moon Europa, astronomers hypothesize that chloride salts bubble up from the icy moon's global liquid ocean and reach the frozen surface where they are bombarded with sulfur from volcanoes on Jupiter's largest moon, Io."

Read more at:
http://phys.org/news/2013-03-astronomers-w...-ocean.html#jCp
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