Simply Astonishing: Enceladus, the Jet-Powered Moon


What an astonishing view of Saturn’s moon Enceladus, as seen by Cassini! At least four different plumes of water ice are spewing out from the south polar region, highlighted because of the black space behind the Moon. On Twitter, Carolyn Porco said that we see four jets because we’re looking down the four tiger stripe fractures crossing the south pole. “How lovely it is to know!” she added.

Cassini was about 617,000 kilometers (383,000 miles) away from Enceladus when it captured this image.

More info: Cassini website

11 Replies to “Simply Astonishing: Enceladus, the Jet-Powered Moon”

  1. Now WHY would Enceladus do that? Cryovolcanoes fed by gravitationally generated heat? or perhaps even magnetically constrained convection in a superconducting fluid?

  2. I pondered the effect on enceladus’ orbit too. I concluded that to the extent that the ejecta is eventually recaptured, the jets will not change the orbit in the long run. If the material achieves escape velocity, or is captured by Saturn, the orbit necessarily will be changed. Not that we’re likely to notice.

  3. IIRC it’s just hot water. (And in vacuum it does not even have to be that hot)

    Tiktaalik – nice point, though once you leave 2-body systems, weird things can happen. I once saw a scheme by which two balls, tied with a string, can lift themselves in orbit using a convoluted tidal maneuver, and slow down the planet in the process. (not to worry, it didn’t turn out to be a useful trick)

    Similarly, you could spew out gas in one direction, and by the time you collect if back from its orbit around Saturn, you collect it equally in all directions, so there is a net thrust. But somehow it has to transfer to the much larger Saturn, since obviously the entire Saturn-Enceladus-vapor system has to remain inertial.

  4. I gather the consensus is on (relatively) hot water. You know, the usual horse, none of Aqua zebras. You think those who think zebras would realize they don’t see zebras/aren’t in dreamland Africa – but that thought itself is a zebra. Sigh!

    Speaking of which, I think Tiktaalik got this correct. Other effects seems contrived.

    But to add to the list of weird gravitational phenomena, apparently you can make sundry “anti-gravity” GR crawlers out of gravitational two-body systems within a third body’s gravity. I can’t remember if they considered momenta changes in the larger body, but the effect is minuscule/not useful. IIRC it would take days or years to move perceptibly. (But damn if I can find the paper now. It was on arxiv – so it must be true. :-/)

  5. Oops. “you collect it equally in all directions” (Yes, mostly I think, the “windshield” effect is likely smaller.) That could be it, though.

  6. Another correction: “it would take days or years to move perceptibly” – it would take days or years to change orbit perceptibly. So its likely the same thing that CrazyEddieBlogger already mentioned, sorry. Man, I need my coffee bad today!

  7. Yeah, you’re right, windshield effect is there and small – I should have said “independently of where the jets were thrusting towards”… “equally” was just shorter and sloppier 🙂

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