Cassini: Enceladus Jets -- Surprises in Starlight

[bystander]

Enceladus Jets: Surprises in Starlight
NASA | JPL-Caltech | Cassini | 2016 May 06

[img3="Narrow jets of gas and icy particles erupt from the south polar region of Enceladus, contributing to the moon's giant plume. A cycle of activity in these small-scale jets may be periodically lofting extra particles into space, causing the overall plume to brighten dramatically. Credit: NASA/JPL-Caltech/Space Science Institute"]http://photojournal.jpl.nasa.gov/jpeg/PIA11688.jpg[/img3][hr][/hr]

During a recent stargazing session, NASA's Cassini spacecraft watched a bright star pass behind the plume of gas and dust that spews from Saturn's icy moon Enceladus. At first, the data from that observation had scientists scratching their heads. What they saw didn't fit their predictions.

The observation has led to a surprising new clue about the remarkable geologic activity on Enceladus: It appears that at least some of the narrow jets that erupt from the moon's surface blast with increased fury when the moon is farther from Saturn in its orbit.

Exactly how or why that's happening is far from clear, but the observation gives theorists new possibilities to ponder about the twists and turns in the "plumbing" under the moon's frozen surface. Scientists are eager for such clues because, beneath its frozen shell of ice, Enceladus is an ocean world that might have the ingredients for life. ...

Stellar Occultation Offers New Insights on Enceladus’ Geysers
Planetary Science Institute | 2016 May 06

[Sheerlook]

Closer to another moon Dr. Watson? Approaching it's furthest distance from Saturn, at it's furthest distance, or just passed its furthest distance? On which side, my dear Watson, of Enceladus do the stronger jets appear, on the side facing Saturn or side away from Saturn, or indeed at right angles to Saturn? Too many questions left unanswered in the apod blurb, Mr. Watson. Send them a formal request for more information.

[neufer]

[b][color=#0000FF]Artist's impression of a global subsurface ocean of liquid water[/color][/b]

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Closer to another moon Dr. Watson? Approaching it's [sic] furthest distance from Saturn, at it's furthest distance, or just passed its furthest distance? On which side, my dear Watson, of Enceladus do the stronger jets appear, on the side facing Saturn or side away from Saturn, or indeed at right angles to Saturn? Too many questions left unanswered in the apod blurb, Mr. Watson. Send them a formal request for more information.

Elementary, my dear "Sheerlook."

It's from the South Pole when that tide is the highest(; i.e., at its furthest distance from Saturn).

[Ann]

Bear with me, Art. Why is the tide highest when Enceladus is at its furthest distance from Saturn (at "apsaturn")?

To me it seems quite logical that the tide would be highest when Enceladus is as close to Saturn as it gets.

Ann

[neufer]

Bear with me, Art. Why is the tide highest when Enceladus is at its furthest distance from Saturn (at "apsaturn")?

To me it seems quite logical that the tide would be highest when Enceladus is as close to Saturn as it gets.

When Enceladus is as close to Saturn as it gets (i.e., perisaturn/perikrone) Enceladus is stretched out like an American football along the axis pointing towards (and away from) Saturn. This makes for a low tide in the other four directions.

When Enceladus is as far from Saturn as it gets (i.e., aposaturn/apokrone) Enceladus relaxes making for a high tide in the other four directions.

All six directions will go through high tide and it is not quite clear why the South Pole is the most susceptible (weakest crust? deepest ocean?) but it does explain why the South Pole would be susceptible at aposaturn.

[Ann]

Thanks. OK, aposaturn, I'll try to remember that. (Think I have heard the expression "apogee", too.)

Ann