But would that mission do any science? And would it steal the New Frontiers budget?

http://www.planetary.org/blogs/casey-dreie...-the-cheap.html

That was in response to the Galileo double-exposure false-plume. There are other statements in that paper about the Cook et al "plume":

The best Voyager evidence for the presence of anomalously fresh frost on Europa's surface is from the controversial, 143° crescent "plume" image of Cook et al. [1982, 1983] (Figure 17). In addition to showing an off-limb feature that was inter¬preted as a volcanic event [Cook et al., 1982, 1983], the image shows a conspicuous bright spot on the surface at 34°, 337°. Helfenstein and Cook [1984] measured the photometric con¬trast of the bright feature relative to surrounding terrains and compared it with that measured of the same geographic region viewed at 13° phase. They found that, relative to the surrounding features, the brightness of the anomalous spot increased as the phase angle increased from 13° to 143° phase by more than seven standard deviations above the average surface change. Although Helfenstein and Cook [1984] interpreted this brightness change to be due to active emplacement of surface materials, a more conservative interpretation would be that the feature represents relatively transparent frost that was deposited on Eu¬ropa's surface in recent geological history [cf. Verbiscer et al., 1990; Verbiscer and Veverka, 1990; Verbiscer and Helfenstein, 1998]. McEwen [1986a] suspected that this bright region was not actually anomalous compared to other bright regions on Europa which had not been seen at high phase angles by Voyager. Indeed, in low-phase global-scale Galileo images, this area appears similar to other bright plains regions.

Figure 17. Unprocessed Voyager 2 clear filter image (FDS 20767.37) at a resolution of ~44 km/pxl and phase angle of 143°, argued by Cook et al. [1982, 1983] to show an active plume along Europa's bright limb. Stretched inset image shows detail of the bright limb and putative plume, and an unusually bright area on the surface. The "plume" feature, with a signal level of just 5 DN, is not observed in subsequent images. Its location in the corner of the Voyager vidicon image, where noise and distortion are most severe, suggests that it is a camera artifact.

Back in December, there was discussion of the available imaging data for the reported plumes region. A blog entry has just been published by Lorenz Roth describing the discovery, along with a nice orthographic view of the identified source region. http://solarsystem.nasa.gov/europa/blogs_l...roth_plumes.cfm

The latest edition features a blog by Lorenz Roth, telling his story of finding possible plumes on Europa using the Hubble Space Telescope.

http://solarsystem.nasa.gov/europa/blogs_l...roth_plumes.cfm

Indeed!

Phillips, C.B., A.S. McEwen, G.V. Hoppa, S.A. Fagents, R. Greeley, J.E. Klemaszewski, R.T. Pappalardo, K.K. Klaasen, and H.H. Breneman. The search for current geologic activity on Europa. J. Geophys. Res., 105, 22,579-22,598, 2000.

"An interesting side note is that one of the images taken in
another imaging sequence on orbit E19 had what appeared upon
initial inspection to be a limb haze just off the bright limb of
Europa. frame s0484R88253 is shown in its raw, unprocessed
(just contrast-enhanced) form in Figure 2a, and a cutout of just
the limb, with a hard stretch, is shown in Figure 2b. The
potential limb haze is visible in figures 2a and 2b as a bright
feature paralleling the limb ~100 km above the surface, at a
brightness level -7% of the average surface brightness. There
was originally much guarded excitement when this image was
received on the ground, but the fact that the "haze" brightness
seemed to exactly parallel the limb brightness, and that the
"haze" was not visible in immediately adjacent images, led the
Galileo engineering team to search tor another possibility. The
match between haze and limb brightness patterns suggests the
possibility of a double image or "ghost image." This possibility
is demonstrated in Figure 2c, which shows a simulated ghost
image constructed by offsetting and adding a dimmer version of
the actual image in 2b, shifted 16 pixels to the left.

"Examination of the imaging sequence and the operation of the
SSI camera itself reveals a likely cause. The image was taken in
the Al8 camera mode, which has a fast frame time and thus does
not reset the charge-coupled device (CCD) detector by
performing a full light flood and erasure cycle in between
exposures [Klaasen eta!., 1997]. This mode also has a reset of
the shutter blades 0.2 seconds before the exposure begins. In all
other imaging modes, the light flood and erasure take place
between the shutter reset and the exposure, but since this
particular mode has no light flood, this docs not occur. The
location and brightness of the offset "ghost image" in frame
s0484888253 are consistent with a small light leak equivalent to
about 0.5 ms of exposure during the shutter reset stage of image
aquisition, which occurred during a slew from the position of the
previous image to this position. The direction and speed of the
slew are consistent with the position of the "ghost image.'' The
light leak would not be noticeable unless the many conditions or
this image were met, namely, the platform slewed from one
position to the next; the exposure time was short enough that the
slight light leak was visible next to the full image; and the image
contained a high-contrast feature (the limb) against which the
ghost image is obvious. The last two frames of the first swath of
plume search images (s04R4889846 and s0484889849) also show
a ghost image of the limb that is consistent with the shutter reset
light leak theory. Only four other images taken during the
Galileo orbital mission have the characteristics necessary (camera
mode, high-contrast boundary, short shutter time, platform
slewing) to detect ghost images produced during the shutter reset;
of these, ghost artifacts consistent with this theory were detected
in three of them."

And from the USGS global map (colorized).

The area of interest is along 180 lon; the authors say 55 and 75 south lat. This is near the boundary between the Galileo E14 global color imaging and G7 global image. Completely coincidentally, the image that shows the area best in one image is the one released the other day, with the comet crash story:
http://photojournal.jpl.nasa.gov/catalog/PIA17658
That two-frame mosaic is from E17, obtained for global shape.
Ted Stryk has a pretty version here: http://planetimages.blogspot.com/2012/05/e...other-take.html

The Europa Clipper currently has 10 flybys at high southern latitudes, and the study team is examining what it would take to do a targetted campaign.

Bjorn,

These are beautiful! There is one more not to forget: a color Europa mosaic on I33. Ted Stryk shows it here:

http://planetimages.blogspot.com/2005/09/i...-snapshots.html

Cheers,
-vexgizmo

The second Europa blog installment is out: A preview of the Europa talks at AGU:

http://solarsystem.nasa.gov/europa/blogs_europa_agu_2013.cfm

Also, there is a Europa-related press briefing scheduled at AGU for Thursday morning at 8 a.m. Stay tuned for what is sure to be some fascinating news.

Check out the new Europa blog on NASA's Solar System Exploration website:

https://solarsystem.nasa.gov/europa/blogs.cfm

The first installment, by Cynthia Phillips of SETI, is a general one about Europa. It includes a color image from Galileo's E19 flyby that wasn't previously released. Look for more to come in the future.

This site is also being updated with information relevant to the Europa Clipper mission concept:
https://solarsystem.nasa.gov/europa/technical.cfm

You got it right. From a Cassini friend: The entire transit spanned from AUG 09 04:00:00 UTC to AUG 12 21:00:00 UTC, with the Sun's center crossing at AUG 11 00:41:06 UTC.

It could simply be that the predicted source location of VII was a bit off the mark. Projecting the jet sources back to the surface is no simple task!

Maybe middle-sized moons, too, if they contain ammonia which acts like an antifreeze.
http://blog.wired.com/sterling/2008/09/involuted-ocean.html

The bluish color is generally associated with large ice grain sizes in clean ice. Ice preferentially absorbs the red light. The "bluish" false-color of Galileo Europa images is attributed to this effect, i.e. absorption of near-IR light.

In the recent press release associated with the regional-scale Enceladus false-color image ("Great Southern Land")
http://saturn.jpl.nasa.gov/multimedia/imag...fm?imageID=3188
the Cassini Imaging Team reports the following:

"Areas that are greenish in appearance are believed to represent deposits of coarser grained ice and solid boulders that are too small to be seen at this scale, but which are visible in the higher resolution views, while whitish deposits represent finer grained ice. The mosaic shows that coarse-grained and solid ice are concentrated along valley floors and walls, as well as along the upraised flanks of the "tiger stripe" fractures, which may be covered with plume fallout that landed not far from the sources. Elsewhere on Enceladus, this coarse water ice is concentrated within outcrops along cliff faces and at the top of ridges."

Me too...

And Slashdot has a similar wrong-headed take on this, based on the New Scientist article.

http://science.slashdot.org/science/08/03/14/1535236.shtml

Can someone with a Slashdot account go set them straight?

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!

Speaking of Io from Europa, I haven't seen much USF discussion of the Flagship study preliminary reports to OPAG last month. Europa's is on line at:
http://www.lpi.usra.edu/opag/may_07_meetin...gship_study.pdf

A careful read shows that 1 m/pixel imaging is advocated with a Narrow-Angle Camera. This would achieve up to 2.5 km/pixel imaging of Io from near Europa orbit. Excellent monitoring is possible indeed, during the 1.5-2.5 years in Jupiter orbit prior to entering Europa orbit. (It's not clear whether the camera would/could be turned to Io during the 90+ day Europa "prime science" orbital mission itself, and the many months to >1 year "extended mapping" phase at Europa which the presentation advocates.)

-vg

Here is the context for this G2 palimpsest observation (this palimpsest is now named Epigeus). Every other frame of this observation, too, contains truth windows. This one is a nice complement to the Memphis Facula observation--each shows a transect across the various palimpsest facies.

Hey... Ganymede could never be fugly!
This shows the context for the light-dark boundary observation. These images, and others that overcompressed, actually look pretty good as soon as they are resampled by reprojection. By the way, every other frame contains a central "truth window"--a 96x96 pixel area where there is no compression at all.

Speak not too soon--and credit Cassini researchers with the discovery:

Energetic neutral atoms from a trans-Europa gas torus at Jupiter
B. H. Mauk, D. G. Mitchell, S. M. Krimigis, E. C. Roelof and C. P. Paranicas
Nature 421, 920-922 (27 February 2003)

Here we report the analysis of ... a torus of emission residing just outside the orbit of Jupiter's satellite Europa. The trans-Europa component shows that, unexpectedly, Europa generates a gas cloud comparable in gas content to that associated with the volcanic moon Io. The quantity of gas found indicates that Europa has a much greater impact than hitherto believed on the structure of, and the energy flow within, Jupiter's magnetosphere.

There is a nice summary of this article here:
Johns Hopkins Applied Physics Lab Researchers Discover Massive Gas Cloud Around Jupiter
http://www.jhuapl.edu/newscenter/pressrele...2003/030227.htm

More from McKinnon, et al. A nice story from the St. Louis Post-Dispatch, plus a couple of nice graphics.

http://www.stltoday.com/stltoday/news/stor...9F?OpenDocument

"We think the ocean leaks onto the surface," said McKinnon, a planetary scientist at Washington University. "What does that tell us about the chemistry of the water that's down below? And the 64 billion dollar question is, could any of that stuff have the signature of life?"

I predict option 1, with a $1B cost cap for New Frontiers, and with a Europa Flagship mission the clear winner a year from now. That would be the right answer, assuming NASA can see through its current Moon-colored glasses.

Analogous to Galileo at Jupiter, I would imagine that Saturn would have to be final resting place of Cassini, given all the discussion of a potentially habitable environment at Enceladus. Like at Europa, we may now have to give a hoot and not pollute.

I count 4--I repeat: at least 4--of these use Ganymede as a generic icy world to represent Pluto. Now which planetary system ought we to be exploring?