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Europa PR, A couple of new posts to the Photojournal
Greg Hullender
post Jan 11 2008, 04:09 AM
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Any thoughts as to what the minimum thickness might be? After all, Earth's crust is pretty thick too, but it does have its thin spots.

--Greg
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rlorenz
post Jan 11 2008, 03:57 PM
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QUOTE (Greg Hullender @ Jan 10 2008, 11:09 PM) *
Any thoughts as to what the minimum thickness might be? After all, Earth's crust is pretty thick too, but it does have its thin spots.

--Greg



Zibi Turtle's finite-element modeling of crater collapse said
the crust had to be '14km minimum' IIRC
(at the location and time of crater formation)

Dr Shank's depth/diameter analysis I think pointed in a similar direction (see also his earlier
post about scarps)
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JRehling
post Jan 12 2008, 07:57 AM
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Ice will not sustain major deviations in thickness for long spans of time, but I think the critical issue is if it can sustain them for a short time. Either a rift or a hot spot (which could mean a plume of slushy ice, or actually water welling up to or near the surface). I think the whole ballgame with Europa is to see if there's a place like that. If so, a submarine is possible. If not, we're stuck with the top few meters to explore.

I think the dark lineation along the triple bands is an indication that water gushed out along a huge number of tremendously long faults. Given the surface age of Europa, that translates into a considerable amount of active fault per year. The trick is whether you get about that much fault all the time, or if you have none at a typical moment, then occasionally much more activity takes place.

But we don't need an actual gusher -- just a place where the 20 km depth has been considerably reduced.
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vexgizmo
post Feb 10 2008, 04:45 PM
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QUOTE (JRehling @ Dec 21 2007, 05:12 PM) *
Incidentally, I think on the first one, they got the apparent motion of Jupiter completely backwards while moreover depicting Jupiter as tidally locked WRT the Sun (or somehow otherwise rotating other than the way it actually does).

The goal was for Jupiter's rotation not to distract from the message, so Jupiter was not rotating at all. Riding along with Europa but with Jupiter not rotating unfortunately gave the false impression that Jupiter was rotating backwards.

This graphic has now been revised showing Jupiter rotating, alleviating this problem, but rotating much slower than actual speed, as to not be overly distracting.
http://photojournal.jpl.nasa.gov/catalog/PIA10149?

Thanks for the feedback!
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JRehling
post Feb 11 2008, 06:34 PM
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QUOTE (vexgizmo @ Feb 10 2008, 08:45 AM) *
The goal was for Jupiter's rotation not to distract from the message


Probably for most people it didn't. But I'm the kind of guy who whispers to the person next to me in the movie theatre if the sun appears too high in the sky for the latitude and season that a scene is set in, or if the sun is on the left of someone who is supposedly driving east in the northern hemisphere. I'm glad that for one, my pedantry had an impact!
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belleraphon1
post Nov 15 2011, 09:45 PM
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NASA Hosting Science Update about Jupiter's Icy Moon Europa
http://www.spaceref.com/news/viewpr.html?pid=35229

NASA will host a Science Update at 1 p.m. EST on Wednesday, Nov. 16, to discuss new theories concerning Jupiter's icy moon Europa. The event will be in NASA's James E. Webb Auditorium at 300 E St. SW in Washington.

NASA Television and the agency's website will broadcast the event live. Reporters may attend the event or ask questions from participating NASA centers or by phone. For dial-in information, reporters must contact Dwayne Brown at: dwayne.c.brown@nasa.gov with their name, media affiliation and telephone number by noon Wednesday.

Europa, which is slightly smaller than Earth's moon, is thought to have an iron core, a rocky mantle and an ocean of salty water beneath its frozen surface.

Briefing participants are:

- Britney Schmidt, postdoctoral fellow, Institute for Geophysics, University of Texas at Austin
- Tori Hoehler, astrobiologist and senior research scientist, NASA's Ames Research Center, Moffett Field, Calif.
- Louise Prockter, planetary scientist, Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
- Tom Wagner, program scientist, cryospheric sciences, Earth Science Division, NASA Headquarters

For NASA TV streaming video, scheduling and downlink information, visit: http://www.nasa.gov/ntv

For more information about NASA and agency programs, visit: http://www.nasa.gov


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antipode
post Nov 16 2011, 03:51 AM
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Lets see, no current assets in Jupiter space, so this either has to be something derived from old spacecraft data, or something derived from current telescopic studies (or a combination of both).

I'd love to see evidence of venting of volatiles from one of those long cycloid cracks a la Enceladus, but...

Any ideas?

P



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nprev
post Nov 16 2011, 05:06 AM
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I'm not reading this as a brief on new results; seems more like a presentation of new theories on the subsurface.


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DrShank
post Nov 16 2011, 06:16 PM
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Getting at the ice shell thickness has been a real problem. All our evidence is circumstantial. But there are mountains a kilometer
high and
basins a kilometer deep. the surface is warped and the craters need to get very large before they start to penetrate near the bottom.
all these things point to a thicker ice shell, likely a minimum of 10 km, possibly as much as 20 km.


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belleraphon1
post Nov 16 2011, 06:37 PM
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Really is a conundrum... to me. I just wonder how you get enough energy from warm (hot) water plumes in the underlying ocean to penetrate through kilometers of steel hard ice. Yet the topography demands a thick ice shell.

Cool problem smile.gif

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DrShank
post Nov 16 2011, 06:51 PM
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agreed. the new model and even the diapir model rely on warm ice from the base of the shell rising upward in a dome, like porridge boiling on a stove. water plumes melting through this thick ice is very difficult indeed, but doing it within the shell, thats easy(ier)


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belleraphon1
post Nov 16 2011, 06:58 PM
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So we are still talking plumes of warm ice... even in this new model. Yet the matrix looks like it needs melted ice (water) to explain the chaos. I am probably missing something. Are we talking a mechanism that lets melt (water) migrate to the top? Guess I really need to read the paper!

Thanks Dr Shank!
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DrShank
post Nov 16 2011, 07:02 PM
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its a difficult concept even for me, but the rising plume changes the conditions of the ice over it. melting is a function of pressure as well as Temp,
and this causes a zone of ice to melt over the plume. yes it all takes place within the shell itself


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belleraphon1
post Nov 16 2011, 07:13 PM
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Interesting. And I guess there are chemical condistons relating to the saltiness and other constiuents in the melt (sulpuric acid, etc). And in the top icy layer pelted with Io
breath (sulphur).

Nature sets up grand experiments...

Thanks again!
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Paolo
post Nov 16 2011, 07:14 PM
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for the lucky few having access to Nature, the paper is here:
Active formation of ‘chaos terrain’ over shallow subsurface water on Europa


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I'm one of the most durable and fervent advocates of space exploration, but my take is that we could do it robotically at far less cost and far greater quantity and quality of results.

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