Timeline at: Planetary Society Weblog: Cassini flies within 25 kilometers of Enceladus tomorrow

Closest approach
2008 October 09, 1207 PDT, Thursday
2008 October 09, 1507 EDT, Thursday
2008 October 09, 1907 UTC, Thursday

4-1/2 hours to closest approach

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Timeline at: Planetary Society Weblog: Cassini flies within 25 kilometers of Enceladus tomorrow

Coming up now:

45 minutes past closest approach

===

From the inbound: Planetary Photojournal: Focus on Enceladus

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There will be a series of DPS40 talks on Enceladus, live-streamed, today at 2:30 EST.

The link to the stream is:
http://cornellmediasite.cit.cornell....playerType=WM7

Considering, and rejecting, Department of Public Sanitation, my mind turned to a faint memory of Emily Lakdawalla recently mentioning some meeting with webcasts.

Planetary Society Weblog: Cassini flies within 25 kilometers of Enceladus [October 9]

Such as (times EDT):

Edit: I tried the "Dynamical Classification of Planetary Bodies" which should have started half-past the hour, but all I get is "Waiting for presentation to begin". It's 20 minutes late (now) or something's not working or misscheduled.

DPS 40, the 40th meeting, AKA DPS08, has a website at Cornell: 40th annual meeting of the Division for Planetary Sciences of the American Astronomical Society

Edit: Something's not working. But something else is, in the wrong place. I found, underway:

Dynamical Classification of Planetary Bodies: http://cornellmediasite.cit.cornell....9-6f48d0706d61

at:

Enceladus: http://cornellmediasite.cit.cornell....b-ded936f07705

Edit: They swapped the URLs for the above two.

Enceladus presentation is at: http://cornellmediasite.cit.cornell....9-6f48d0706d61 and the webcast is on now, but the speaking hasn't quite started. Edit. Wait. No, it looks like a repeat the "Dynamical Classification of Planetary Bodies" talk at that URL (but the viewer software calls it "Enceladus"). Grr. Where's Enceladus?

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http://cornellmediasite.cit.cornell....playerType=WM7

The links in the program got transposed.

There will be a series of DPS40 talks on Enceladus, live-streamed, today at 2:30 EST.

What defines a planet? :
http://cornellmediasite.cit.cornell....playerType=WM7

Enceladus:

http://cornellmediasite.cit.cornell....playerType=WM7

Right now, that should be Enceladus. The title in the viewer is "Enceladus". But it's the 4-speaker presentation on dynamic classifications of planets, recently done live.

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Right now: Enceladus: http://cornellmediasite.cit.cornell....9-6f48d0706d61

Viewer has it entitled: "Special Session: Dynamical Classification of Plantary Bodies" but it's Enceldaus right now. Later it may be a replay of planet classification. It's live, Enceladus now.

I should add that later, also, it may possibly be a replay of the Enceladus presentation.

The Cornell Mediasite I presume, from a small sampling, has channels for presentations. If the live webcast hasn't begun, a slide tells you it hasn't started. If you come in later, it replays a record of the live presentation from earlier. If you're lucky. And if the URLs aren't swapped between two different presentations, and the phase of the moon is just right.

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An interesting set of talks.

Now, it seems the heat is climbing upwards to 13 GW. There may be a heat transition in one of the stripes, but it is too early to be sure of this. The high resolution pass gave lower (around 167K) compared to an earlier pass (187K). There is a pressure constraint that impacts on the "Cold Faithful" and Nimmo friction theories. There seems to be a large error in determining the age of the stripes. From one consideration they might be over 3 billion years old, but from cometary impacts only 400 million years or less. Tidal stress and libration can give heat, but it is unusual that it is not over the entire moon, like Europa, and only at the South Pole.

(Personal comment: Tidal stresses might not be responsible for the stripes, but they may be important for maintaining them and preventing them from "healing" or freezing up)

The flexing of the stripes might be responsible for the "shark fin" features. There was no discusiion of the October 9 data other than to acknowledge its reception. Perhaps the AGU talks will include this recent data.

Gad, I wish I had wandered into this thread yesterday...or Emily's invitation; I used to read every word in her blog, and I have to do so again. That the Planetary Society can't afford to send her is another troubling sign of the times; so to speak - the very real effect upon those who rely upon donations from the public to function. In many cases, these donations turn into trusts; and the budget is spawned from the revenue yield these trusts. But in a grueling market where trillions of dollars evaporate; so do the revenues from trust funds.

But back to the tiger stripes: The surface temperature measured is a minimal constraint upon the temperature of the engine below. Also, even though the second pass should have had higher resolution (and less of the colder surface mass impinging upon the reading) the 20 deg K increase is really a confirmation of the earlier pass. Amazing phenomenon. If we were truly a geek society; we would have another mission on the way and and at least two more missions planned. It would be interesting (saddening) to know how much more the media spends covering Paris Hilton's faux campaign than it does covering DPS40.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

The Hi-Res readings were the colder readings. Because the instrument works in a non-linear way, they want to check for possible systematics being responsible for the change at Damascus rather than announce the the temperature fall is real. One of the possible models if the change is real is to consider that the heat engine is turned off for just Damascus. This might imply a moving "hot spot" beneath the surface, something similar to how the Hawiian Islands are made.

Also of interest is the identification of relic tiger stripes and offsets where one piece of stripe got separated by faulting from the main relic stripe body. It is sort of like a jig-saw puzzle or rubrics cube where the history needs to be re-assembled by partial rotations which in turn may give some idea of the timescale over which these rotations occured. Maybe one can trace the motions of the "hot spot" by the re-assembly of relic stripes.

According to the VIMS instrument, Titan's lakes are only millimeters thick which means the lakes are actually either dry mudflats or are coated with a thin film of something that block sunlight. No data from north polar lakes available yet, though. Specular reflections may have been seen.

Speaking of north polar lakes, Titan's thick atmosphere bends light which allows Cassini to peek lakes beyond the terminator that have so far been in darkness.

New dark splotches have appeared in the southern polar region suggesting that the lakes there are starting to fill as the southern summer is coming to an end. There apparently have been torrential rains in the recent months.

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Not new, but well done.

Courtesy of BA Blog: The Big Picture: Enceladus

Boston.com does Enceladus up close

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Those pictures are beautiful.

About 30 minutes past Enceladus closest approach.

NASA Enceladus Blog

dmuller has a great countdown and clock page that will provide temporal orientation for this flyby: Cassini Real-Time Simulation

Outbound observations underway.

In about 3 days there is a Titan flyby, 2008 November 3, 1735 UTC. (Roughly. Approaching end of daylight saving time for me is obscuring my vision.)

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BA Blog: Cassini hi-reses Enceladus

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Planetary Society Weblog: Enceladus!

Lots of yummy images there.

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New thermal readings of potential cooling hot spots might help sort out if the temperature change was a systematic or real and if the hot spot has cooled even more since the last flyby. This might help set some constraints on the heating mechanism.

The new images may present some more jig-saw puzzle images for re-assembling relic tiger stripes.

Universe Today: Underground Water Reservoirs Power Geysers on Enceladus

Nature News: Enceladus shoots supersonic jets of water

JPL News: Enceladus Jets: Are They Wet or Just Wild?

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Maintaining a heated ocean by resonance absorption


A recent article published in Nature invokes large amplitude Rossby waves to capture obliquity tidal energy 3 orders more efficiently than normal tidal forces contribute:

Strong ocean tidal flow and heating on moons of the outer planets

Abstract: http://www.nature.com/nature/journal...ture07571.html


Recently, tidal force theory took a hit when it was discovered that the plumes were more active at the wrong place in the orbit of Enceladus. But considering the 3 orders of magnitude increase where the lake is of just the right size to admit the resonance constructively, this may help resolve the Goldilocks problem that makes Enceladus special.

The effect seems similar to the Tesla earthquake machine theory or the anecdote regarding the tenor who sings the correct pitch to shatter a crystal glass that absorbs the energy. Similar is where a key an octave or twelfth above another key on a piano is softly depressed so that only the damper is raised and then the fundamental is struck loudly and then damped; one can hear the energy of the overtones captured by the lightly depressed key. If the fundamental pitch loudly struck does not contain the higher depressed key in its overtone structure, then the energy transfer is much less amplified.

There may be a condition of equilibrium that is attained where the heating causes the lake to grow beyond the harmonic, only to freeze to shrink back to the correct harmonic to then accept the tidal harmonic energy. It tends to be self-maintaining. The plumes may serve as a governor if the heating gets too hot on occasion.

There still remains the problem of how the lake initially formed from solid ice to reach the volume to where resonance absorption can kick in to sustain the heat.

NASA Cassini-Huygens Mission News Release: Saturn's Dynamic Moon Enceladus Shows More Signs of Activity

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Planetary Society Weblog: Ganesa Macula isn't a dome

Surprise!

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Cassini press release:

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"The presence of extensive cloud systems covering the area in the intervening year suggests that the new lakes could be the result of a large rainstorm and that some lakes may thus owe their presence, size and distribution across Titan's surface to the moon's weather and changing seasons."

Suggestions should always be taken with a grain of caution: If you've been around long enough, you know how certain we were that there was plant life, growing and ebbing on Mars ~50 years ago.

I don't object to methane rains on Titan, but I think if there is a vibrant methane cycle, we should have found higher concentrations of ethane and other more complex organics during Huygens descent, especially in the lower atmosphere and very near the surface, and that the concentrations of these hydrocarbons on the surface should be black, not red: Organics polymerized by uv turn black. I think that the methane in the atmosphere on Titan, wherever it is coming from; is gradually escaping rather than concentrating and raining, just as it is on Mars. The colors are all wrong.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

Two Iapetus videos:

Cruising with Pan

'Saturn's small, walnut-shaped moon, Pan, embedded in the planet's rings, coasts along in this movie clip from the Cassini spacecraft.'

Cassini press release:

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Everything I need to know I learned through Googling.

Yet another amazing animation, this one compiled from the raw JPEGs by Bill Harris over at UMSF.com:
Janus undergoes an inverse eclipse, passing through the narrow slot of sunlight filtering through the Cassini Division.

Perhaps this has been mentioned here (it's a long thread), but in attending a panel at DragonCon yesterday given by four JPL Cassini-Huygens team members, I learned how they propose to end the spacecraft's mission. The concern is that if left to it's own devices after the propellant is exhausted, it might potentially impact one of the icy moons. The heat generated by the RTG might create a pool/puddle of liquid whatever where there had been none before and introduce an undesired variable in the local environment.

So, the proposal is to use the last of the fuel to whip the craft around Titan in such a way as to cause Cassini to go between the rings and the planet (there's just 3000 km safe separation), gather important data not available otherwise and then have it impact the planet on a subsequent go-round.

"The heat generated by the RTG might create a pool/puddle of liquid whatever where there had been none before and introduce an undesired variable in the local environment."
...
"impact the planet on a subsequent go-round."
And this will NOT introduce an undesired variable in the local environment?

I personally say, go to Saturn - close and personal.

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