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Water plumes over Europa
stevesliva
post Sep 7 2018, 12:44 PM
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QUOTE (HSchirmer @ Sep 6 2018, 07:27 PM) *
vertical ice-pipes


You mean like penitentes? Wikipedia calls them "almost a black body"
https://en.wikipedia.org/wiki/Penitente_(snow_formation)
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HSchirmer
post Sep 7 2018, 06:08 PM
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QUOTE (stevesliva @ Sep 7 2018, 01:44 PM) *
You mean like penitentes? Wikipedia calls them "almost a black body"


Well, conceptually similar -
ice structures grow due to "phase change" as water forms ice and accumulates in areas with higher heat loss.
But penitenties are sublimation and radiative heat loss to the sky, while ice pipes are snowpack melting and conductive heat loss to the ground.

So, practically, think "upside down penitentes".

Found it- red aeolian dust changes how snowpacks melt-

the variation in ice column morphology between red and clean snow gives insight into how dust deposition events may affect the energy balance, subsequent melt, and meltwater flowpaths in snow covered areas

The movement of liquid water through the snowpack in “red” snow thus appears to be more uniform, decreasing the size of preferential flowpaths that give rise to ice columns.
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rogelio
post Oct 9 2018, 12:41 PM
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QUOTE (HSchirmer @ Sep 7 2018, 12:08 PM) *
Well, conceptually similar -
ice structures grow due to "phase change" as water forms ice and accumulates in areas with higher heat loss.
But penitenties are sublimation and radiative heat loss to the sky, while ice pipes are snowpack melting and conductive heat loss to the ground.

So, practically, think "upside down penitentes".

Found it- red aeolian dust changes how snowpacks melt-

the variation in ice column morphology between red and clean snow gives insight into how dust deposition events may affect the energy balance, subsequent melt, and meltwater flowpaths in snow covered areas

The movement of liquid water through the snowpack in “red” snow thus appears to be more uniform, decreasing the size of preferential flowpaths that give rise to ice columns.


Penitentes up to 15 m high, spaced 7.5 m apart at the equator? Challenging for a lander...

https://www.nature.com/articles/s41561-018-0235-0

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stevesliva
post Jul 25 2019, 02:22 PM
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First bright stellar occultation for Europa:
http://sci.esa.int/gaia/61491-astronomers-...thanks-to-gaia/

Relevant to this thread because the Hubble data was, I think, derived from Europa occulting Jupiter.

Surprised it's the first!
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Jaro_in_Montreal
post Nov 18 2019, 07:31 PM
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Today's announcement:

https://www.nasa.gov/feature/goddard/2019/n...vapor-on-europa
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JRehling
post Nov 19 2019, 05:45 AM
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This is an exciting result. The intermittent nature of the plumes may create a challenge for Europa Clipper to sample them without some flexibility to alter the mission in response to unpredictable events.
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Julius
post Jun 25 2020, 10:42 AM
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I still cannot come to terms with the idea that Europa has moved from tectonics (ridge formation) onto chaos as the ice crust has thickened over its 4 billion year history. I guess radar should tell us a lot about what is actually happening.
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JRehling
post Jun 27 2020, 05:27 AM
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From Nimmo and Manga (2009):

"The manner in which Europa’s shell and interior evolved to their present-day states represents a major unsolved problem for at least three reasons. First, the present-day state, especially of the silicate interior, is poorly known. Second, Europa’s surface may only record the last 1% of its existence, so there are few constraints on its earlier history. Third, the thermal and orbital evolution of Europa are intimately coupled in a manner that is nontrivial to model."

https://websites.pmc.ucsc.edu/~fnimmo/website/draft5.pdf

One significant work since then was the melt-lens model of Schmidt, et al (2011):

https://www.nature.com/articles/nature10608?proof=trueNov

In a nut [ice] shell, the internal dynamics and certainly the history of Europa's ice shell are far from determined, although the tidal forces that create the most visible linea have probably been modeled well.

Even after one or several more missions, I doubt if we will have good information about the history of Europa's ice shell pre-dating that "last 1%" but finding out what's going on there now is something I'm very much looking forward to.
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StargazeInWonder
post Jul 12 2022, 05:58 PM
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This is just a teaser for now, but JWST will attempt to detect and characterize any Europa plumes, which were detected, but at low signal, by HST, and were detectible only sometimes. JWST has the capability to detect spectral features that HST is simply not capable of, those above 2.5 microns. That corresponds to CO2, among other possible components. Of course, what it actually detects will depend on what, if anything, is actually there when it observes.
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Decepticon
post Oct 6 2022, 03:01 AM
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^ I was unable to find observation dates on this.

Has this already occurred?
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StargazeInWonder
post Oct 6 2022, 04:16 AM
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This indicates that the first observations are planned for November and December, 2022.

https://www.stsci.edu/jwst/science-executio...on.html?id=1250

Jupiter is just past opposition now, so it will be a bit farther than is optimal when the observations are made; I guess the competition for observing time led to the later dates. Also, there are constraints on the observations as they will want Europa to appear far from Jupiter's disk. Also note that this same observation program, 1250, includes observations of Enceladus.
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Explorer1
post Oct 6 2022, 06:58 PM
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I recall that JWST cannot be pointed directly away from the Sun, so it cannot never take opposition period images of any outer planet (though at such distances its not a major issue, I think).
See here: https://jwst-docs.stsci.edu/jwst-observator...ing-constraints
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