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Water plumes over Europa
marsbug
post Dec 12 2013, 04:55 PM
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This seems like the relevant place to post this (could be wrong): Water plumes from Europa? Apologies if it's already been up. The link to the Science article at the bottom doesn't work for me, does anyone have a working link to the original? Cheers.


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Hungry4info
post Dec 12 2013, 05:08 PM
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Here's a link to the paper.
http://hubblesite.org/pubinfo/pdf/2013/55/pdf.pdf


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JRehling
post Dec 12 2013, 07:20 PM
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Apparently, Europa joins Enceladus in having active water plumes observable in the present.

http://www.sciencemag.org/content/early/20...science.1247051

This might suggest tailoring exploration plans, already in progress, to focus on the study of these plumes, if they are continuous enough to be active when a putative mission could observe them in situ.
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marsbug
post Dec 12 2013, 08:32 PM
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QUOTE (Hungry4info @ Dec 12 2013, 05:08 PM) *

Thank you!


Moderator note: Two topics merged. Quote added at the top of this post to make its context clear.


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JRehling
post Dec 12 2013, 09:27 PM
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The modeled density is comparable to that of plumes at Enceladus. Campaigns to observe plumes over Europa visually failed, which may indicate simply the transience of such activity, although the schedule of the transience becomes extremely interesting. If there is outgassing at some point during every (or nearly every) orbit, then any jovian orbiter with Europa flybys could observe the plume in situ, if the tour is designed appropriately. If the outgassing is rarer, or unpredictable, then that makes in situ observation a challenge.

An extraordinarily interesting possibility here is that the source of Europa's plumes may involve water in contact with a sub-surface ocean floor, which could make the chemistry arbitrarily complex, whereas some models of Enceladus's plumes indicate that the source may be surrounded by more ice on all sides, which limits the possible chemistry.

The lens-melt model of Europa's ice argues that the evidence of surface/melt-through contact occurs between lakes of water which are not in direct contact with the ocean, but exist between the ocean and the top of the ice. This would be of greater interest if the ice that melted to form those lakes had been part of the ocean previously (especially if they were in contact recently).

The proposals for the Europa Clipper mission include a neutral mass spectrometer making flybys of <1000 km to sample the Europa atmosphere. The new discovery, and follow ups, may suggest a different trajectory, but that instrument is already part of the package. The proposals suggest a launch of 2021 or 2022, although that seems tentative.

The possibility of a free-return trajectory sample return bringing some of these plumes to Earth is extremely exciting. A sample return from Europa's surface would be very challenging. The free-return option is much, much more modest in terms of delta-v.
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Bjorn Jonsson
post Dec 12 2013, 10:02 PM
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I have now taken a quick look at the article. An enhanced emission was detected near 90 west longitude. Here is a quick and dirty orthographic render of Europa's southern hemisphere:


Attached Image


If I understand the article correctly the most likely location for the plume source is near longitude 90W in the far south. As the render above shows, most of the terrain in the area of interest isn't very well imaged although there is a narrow swath of good images near 90W.

There are some Europa diagrams near the top in this interesting blog entry at the Planetary Society website but the diagrams are rather fuzzy and it's not completely obvious to me what they are showing or where - possibly the location of a likely source region.

It will be interesting to see how this affects the JUICE plans. Plumes like this one should be easily detectable by JUICE - the problem is if they are transient. As currently planned, the closest approach occurs approximately over Thrace and Thera Macula (in the image above, the two dark spots near bottom at 180W).
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nprev
post Dec 12 2013, 10:14 PM
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I think this finding dramatically strengthens the case for what would essentially be Galileo Mk 2. It's quite possible that ALL the major Jovian satellites experience transient activity.

Europa is of particular interest, of course, but a mission with broader objectives would be much more likely to fly.


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0101Morpheus
post Dec 12 2013, 10:31 PM
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I think only Europa is the only moon with a thin enough crust to sustain geysers though. But who knows? Maybe Ganymede had geysers billions of years ago.

I can't wait until JUICE is launched. Absolutely one of the most exciting planetary missions of the next decade.
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rlorenz
post Dec 12 2013, 11:38 PM
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QUOTE (JRehling @ Dec 12 2013, 04:27 PM) *
An extraordinarily interesting possibility here is that the source of Europa's plumes may involve water in contact with a sub-surface ocean floor, which could make the chemistry arbitrarily complex, whereas some models of Enceladus's plumes indicate that the source may be surrounded by more ice on all sides, which limits the possible chemistry.


But for the chemistry to be interesting, there must be available carbon. There is little evidence of any on Europa, and models of the protojovian nebula have it too hot to incorporate much. So yeah, if sulphates are your thing, then Europa is demonstrably great. Prebiotic chemistry may be a very different matter.
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elakdawalla
post Dec 12 2013, 11:39 PM
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Wouldn't infalling comets deliver carbon to Europa as they do to other places in the solar system?


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nprev
post Dec 13 2013, 01:19 AM
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I wonder about that. Certainly the Jovian system gets more than its share of comet & asteroid impacts...what have we seen, two or three since the early 1990s, now that we know what we look for?

I don't see why Europa could not have obtained abundant carbon from these infalls. We seemingly don't have any way to assess its impact history any further back than 10 million years or so, which is not surprising for what seems to be a dynamic surface environment.

I look forward to any sort of exploration of this moon. There are a LOT of questions to be answered, and doubtless we'll have even more later.


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Juramike
post Dec 13 2013, 03:31 AM
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QUOTE (rlorenz @ Dec 12 2013, 07:38 PM) *
So yeah, if sulphates are your thing, then Europa is demonstrably great. Prebiotic chemistry may be a very different matter.


Which is one of the very reasons Europa might be so interesting. At absolute worst it might all be hydrothermal vents and energy, with no organics.
Compare/contrast with Titan: abuncha cool-o organics, but no obvious hydrothermal system to throw in energy. (proposed in one model, but not yet observed.)

And sulfur/sulfates iron(II)/iron(III) are excellent start points. Anywhere there is a chemical disequilibrium is exciting.


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marsbug
post Dec 13 2013, 12:03 PM
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A habitable environment without life would be very useful as a comparison to habitable environments with life. Not as headline and budget friendly perhaps, but scientifically just as good.


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vjkane
post Dec 13 2013, 03:36 PM
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Looking at smaller missions than ESA's JUICE or the proposed Europa Clipper, there have been at least two proposals to explore Enceladus with Discovery-class missions. One, JET would image the tiger stripes with a high resolution thermal instrument and sample the plume chemistry with a duplicate of the Rosetta mass spectrometer (much more capable than Cassini's spectrometer). The other would return samples collected in aerogel a la Stardust. I suspect that the concepts could be easily adapted for Europa with the added advantage of being able to use solar power instead of an MMRTG.

Does anyone know whether JUICE would be lucky enough to encounter Europa at its apojove when the plumes (if confirmed and if persistent) are likely to be active?


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elakdawalla
post Dec 13 2013, 04:19 PM
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QUOTE (Bjorn Jonsson @ Dec 12 2013, 02:02 PM) *
I have now taken a quick look at the article. An enhanced emission was detected near 90 west longitude. Here is a quick and dirty orthographic render of Europa's southern hemisphere:

Attached Image

If I understand the article correctly the most likely location for the plume source is near longitude 90W in the far south. As the render above shows, most of the terrain in the area of interest isn't very well imaged although there is a narrow swath of good images near 90W.

There are some Europa diagrams near the top in this interesting blog entry at the Planetary Society website but the diagrams are rather fuzzy and it's not completely obvious to me ...

Thanks for making that orthographic image. Here is a higher-resolution version of the graphic that I put in that blog entry. It shows a model for stresses along cracks near the south pole when Europa is at apoapsis. Can you identify which specific images contain these cracks?
Attached Image


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