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Hubble observations of Ganymede, Teleconference on March 12, 2015
JRehling
post Mar 10 2015, 06:13 AM
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http://www.nasa.gov/press/2015/march/nasa-...n/#.VP6JwEJBDjI

This seems to hint at something momentous. Ganymede hasn't been breaking news very often since the Galileo mission ended, so what's the announcement?

I would think that HST observations of Ganymede could only be worthy of a teleconference if it's one of these:

1) The existence of plumes/geysers as were observed at Europa.
2) Something interesting detected in Ganymede's very-thin atmosphere.
3) Something interesting deposited in the ices on the surface.

One of the speakers, Joachim Saur, has had publications regarding Ganymede's surface, aurorae at Io, Enceladus, and was on the paper announcing plumes at Europa.

Maybe we've got another Galilean with a buried ocean that sprays its contents skyward?
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Hungry4info
post Mar 10 2015, 07:31 AM
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It's probably this and this.


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paul_wi11iams
post Mar 11 2015, 05:18 PM
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QUOTE (JRehling @ Mar 10 2015, 08:13 AM) *
what's the announcement?

The Nasa page says
QUOTE
These results will help scientists in the search for habitable worlds beyond Earth.

Maybe one of your answers is right and this led to an upwards re-evaluation of the input energy needed to explain the thermal output from Ganymede. If tidal effects from forced libration were insufficient, then researchers may have needed to opt for a radioactive source from a long-lived radioactive isotope.

Generalising, they would then find that very long-term radioactivity solves a similar problem for Ceres. The timing of the Ganymede conference would thus be very astute by bringing energy balance into the limelight. NASA might even get lucky by discovering another thermal imbalance around Pluto this summer.

Whatever, their argument would be to suggest that other cold worlds far from their star (and even orphan planets) would also benefit from a similar heating mechanism.

And so to a paradigm change for habitability without a habitability zone. Well, its just an idea. We'll see tomorrow !


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ynyralmaen
post Mar 12 2015, 05:03 PM
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More info here: (and a google hangout in a couple of hours' time)

http://hubblesite.org/newscenter/archive/releases/2015/09
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Hungry4info
post Mar 12 2015, 05:03 PM
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NASA's Hubble Observations Suggest Underground Ocean on Jupiter's Largest Moon
http://www.nasa.gov/press/2015/march/nasa-...n/#.VQHGavnF8rU


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Y Bar Ranch
post Mar 12 2015, 06:02 PM
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I dream of the day when I can buy bottled water from various different planets and moons.

Be nice if a meteorite was on an intercept path with one of these bodies and we could witness the plume following impact.
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Paolo
post Mar 12 2015, 06:47 PM
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is the paper available somewhere on the net? I thought it would be in today's Science but it's not there...
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katodomo
post Mar 12 2015, 07:55 PM
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Saur's research group tends to publish in the (AGU) Journal of Geophysical Research / Space Science section, which is where you can also find it online.

http://onlinelibrary.wiley.com/wol1/doi/10...14JA020778/full
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TheAnt
post Mar 13 2015, 09:45 AM
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The presence of the magnetic field in itself had been seen as one indication of a subsurface layer of salty water. And that's what it is required for it to be electrically conductive to create the field in the first place.

So the detection of aurora is more an indication of how the magnetic field interacts with the environment there.
What bugs me is that illustrations show the aurora as blue. No nitrogen have been detected in the very thin atmosphere of Ganymede.
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katodomo
post Mar 13 2015, 10:32 AM
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At the teleconference Saur corrected this by saying the aurora as seen from the surface would be red.

Should probably be more like orange-red/light red, possibly shifted towards yellow or green too.
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belleraphon1
post Mar 13 2015, 11:37 AM
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Draft of article from the Hubble site http://hubblesite.org/newscenter/archive/r...015/09/related/

The Search for a Subsurface Ocean in Ganymede with Hubble Space Telescope Observations of its Auroral Ovals
http://hubblesite.org/pubinfo/pdf/2015/09/pdf.pdf

Craig
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TheAnt
post Mar 13 2015, 02:50 PM
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QUOTE (katodomo @ Mar 13 2015, 11:32 AM) *
At the teleconference Saur corrected this by saying the aurora as seen from the surface would be red.

Should probably be more like orange-red/light red, possibly shifted towards yellow or green too.


Aha Saur did note that detail also, good of him.

And yes you're right, red is to far to the right in the spectrum. If it strong enough to see with the naked eye, such aurora would be orange-yellow or pink.
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Julius
post Mar 13 2015, 06:31 PM
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The first ever pictures of Ganymede taken by the Voyagers,it was evident there had been tectonic activity. Would a subsurface ocean of liquid water give rise to some form of plate tectonics as on Earth?
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antipode
post Mar 15 2015, 11:22 AM
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Slightly tangential question, but do we have any idea how much protection Ganymede's magnetosphere would provide from Jupiter's magnetosphere for future explorers? I'm thinking particularly about the regions near the equator within closed field lines.

P
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DFortes
post Mar 15 2015, 12:00 PM
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QUOTE (TheAnt @ Mar 13 2015, 02:50 PM) *
And yes you're right, red is to far to the right in the spectrum.


Right, left??? Which way around depends on whether you plot wavelength or frequency on the horizontal axis, and even then if you choose to plot values in ascending or descending order. Maybe we should stick to SI units rather than an entirely anthropocentric reference frame.

QUOTE (Julius @ Mar 13 2015, 06:31 PM) *
Would a subsurface ocean of liquid water give rise to some form of plate tectonics as on Earth?


The low-pressure form of water ice is always less dense than liquid water, regardless of temperature, so cannot founder into the subsurface as cold oceanic slabs do into the Earth's mantle.
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