Enceladus on full afterburner

By Phil Plait | October 1, 2010 9:46 am

This may be my favorite picture of Saturn’s moon Enceladus yet:

enceladus_afterburner

Quick! It’s trying to get away!

My first thought (well, my real first thought was that this is Enceladus on full afterburners) was that this was a composite: two images combined. The moon is icy and very bright, while the plumes of water shooting away from cracks in its surface are faint. But actually, there are two separate light sources here! The face of the Moon we see here is being lit by a full Saturn (think of Saturn as being behind you as you look at the picture). But the Sun is behind Enceladus (not directly behind, but mostly behind and off to the side of the picture), and is illuminating the geysers. That’s why the fainter plumes are visible; we’re looking at the dark side of the moon! If Saturn weren’t lighting it up, the moon would look much darker, and the plumes would be even more visible.

I love how the plumes look like a rocket exhaust. With the moon itself just a little offset in the picture, a little above the center, our brains make it look like it’s jetting up, up, and away!

But don’t worry about it actually rocketing into the wild black yonder. I’ve seen various estimates for the amount of water erupting away in the plumes, but a reasonable amount is about 250 kg/sec, or a ton of water every 4 seconds. That may sound like a lot, but a ton of water is only a cubic meter*!

Enceladus has a mass of about 1020 kg, or 400 quadrillion times the mass it loses from the geysers per second! So even though this picture looks dramatic, the amount of mass Enceladus is losing is actually, and almost literally, a drop in the bucket… but still, enough to resupply the ice particles in Saturn’s diffuse E-ring. Amazing.


* And while some of the material does escape into space, acting like an extremely weak rocket, a lot of it falls back onto the surface of Enceladus. Those particles can’t move the moon, any more than pulling up on your shoes can make you fly.

Credit: NASA/JPL/Space Science Institute. Tip o’ the cosmic umbrella to Carolyn Porco.

Related posts:

Enceladus is erupting!
Cassini dances with Enceladus once again
Enceladus!
Midnight on a ringed world


CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (44)

  1. Steven Vallarsa

    Hey, this is like that cheesy Japanese sci-fi movie from the late 70s, where the bad guys propel their enslaved planet towards Earth. What was that movie called?

  2. Brian Schlosser

    Reminds me of the big spherical lunar landing ship in “2001”

    Any idea of why these geysers are concentrated at the south pole?

  3. Ian Muir

    THAT’S NO MOON! IT’S A SPACE STATION!

  4. Brian Schlosser:

    Any idea of why these geysers are concentrated at the south pole?

    Because the ones on the north pole don’t have enough strength to push so far up. The ones near the south pole are all pointed down, making it easier to escape.

    BA:

    And while some of the material does escape into space, acting like an extremely weak rocket, a lot of it falls back onto the surface of Enceladus. Those particles can’t move the moon, any more than pulling up on your shoes can make you fly.

    Of course they can! The “thrust” of pushing them away moves the moon, and then the force of the particles smashing back down pushes the moon even farther!

    “Conservation of momentum”? “Center of mass”? Never heard of them. Why do you ask?

    :-) :-) :-)

  5. Ian Muir:

    THAT’S NO MOON! IT’S A SPACE STATION!

    You’re thinking of Mimas, not Enceladus.

  6. I see an egg being fertilized. Whatever that says about me.

  7. Aleksandar

    Are you certain that ejecta that falls back does 0 thrust? Its been ages since my mechanics lectures to I can’t visualize entire system accurately.

    Anyway. The particles that are going above Enceldaus escape speed will certainly exert thrust, and also the change of mass of the moon should be shifting its orbit?

  8. Jeff Fite

    Death Star? Aries 1b from 2001? Cheesy planet of enslaved kaiju? Naah…

    Larry Niven fans all recognize the Long Shot. :-)

  9. Brian Schlosser

    @9 Jeff Fite: Of COURSE! Its a General Products Type IV hull! And, given its opaque nature, the statis shield must be on!

  10. Messier Tidy Upper

    Quick! It’s trying to get away!

    Or, worse yet :

    LOOK OUT!!! Its headed right for us! ;-)

    Great picture. :-)

    Enceladus isn’t the twelfth satellite of Saturn is it? It sure looks alive though – where’s Cirocco “Rocky” Jones & Gaby when you need them? ;-)

    * Ref. to John Varley’s ‘Titan” novel case anyone’s wondering.

  11. Peter

    Is it possible for these exhaust plums to have a small effect on the moons orbit?

  12. kkozoriz

    Enceladus:1999

    I think I see Martin Landau and Barbara Bain!

  13. TBRP

    @ Aleksandar

    Enceldaus’ orbit is affected, however it will take about 1000 millenia for the change to be actually noticable (assuming the gysers push at a constant rate for all that time).

  14. It looks fake, almost like someone hung an ice ball from a string then photo-shopped in the “tail.”

    ~Rhaco

  15. Jeff

    that is definitely the most “real time active” phenomenon I’ve seen imaged on a planet other than earth. Maybe only the old Voyager pics of IO come close.

    This solar system really is big and unexplored. I taught earth science 20 years and even today still keep learning things about our home planet, imagine how much is still hidden and may remain hidden from mankind about other worlds. I even read that certain areas of earth such as parts of Alaska are still unexplored. Theme to me is, mankind, all your arrogance stand aside, the solar system will show you your true place in the scheme of things.

  16. Douglas Troy

    Its sprung a leak! Now it’s gonna go flat.

  17. Grand Lunar

    I second the question from post #1; what was the name of that Japanese movie where they put rockets on the Earth to evade a runaway star?
    (geez, can’t believe I remember that after so many years!)

    Anyway, pretty cool! It does look like it’s escaping.

    And here’s an idea; since we had “Space:1999″, this can be “Space:2099″!

  18. QuietDesperation

    What was that movie called?

    Gorath.

    That was off the top of my head, BTW. I saw it on TV as a kid, and there’s a night scene of the ocean and high winds and the moon drifting across the sky as it gets pulled toward Gorath that still sticks with me.

    Wikipedia fills in the details:

    http://en.wikipedia.org/wiki/Gorath

    Hey, this is like that cheesy Japanese sci-fi movie from the late 70s, where the bad guys propel their enslaved planet towards Earth.

    Gorath was a rogue star. Humanity builds giant rocket engines in Antarctica to move the Earth out of the way. Complete awesomeness to me. Well, be fair, I was seven when I saw it. It’s kind of like When Worlds Collide, but with bigger goals.

  19. Gerry

    Low thrust over a long period of time…. uh, kinda like an ION ENGINE???

    Wonder if this will affect the orbit of the moon over very long periods of time?

  20. Brian Too

    Vader to Commander: Make way to reposition the Death St-, er, hello children! Enceladus! I meant Enceladus.

  21. Anchor

    That’s got to be my favorite now too. Wish it had been higher res…but Casini still has plenty of sand in the upper chamber of its hourglass…

    Phil says, “I love how the plumes look like a rocket exhaust.”

    Yes indeed. Gases dispersing into a vacuum. Just like that.

    Generally, however, Hollywood visual effects meisters don’t pay attention to such physics, so they habitually show rocket plumes and explosions as ludicrous BILLOWING phenomenon, with an expulsion of (hot) gases into an air-filled medium, since those are the kinds of effects they think audiences will read as ‘authentic’ exhausts or explosions.

    It is the counterpart phenomenon to the ‘self-fullfilling prophecy”: give the audience what they think they’ll accept as an ‘explosion’ or ‘exhaust’, and the audience will continue to expect the bull.

  22. Astrofiend

    “Quick! It’s trying to get away!”

    Ah – excellent. I was in a funk writing up some stuff for uni, and then I saw this. For some reason, it just cracked me up and made my day.

    Cheers Phil!

  23. Jeffersonian

    Mind-blower. Seriously.

    And, hey…this one’s in my neighborhood!

  24. ggremlin

    Saturn, the space ship parking garage of the solar system.

  25. Andrew

    But Enceladus has been there for thousands of millennia. If this phenomenon lasts that long, it must have has a measurable impact. Perhaps the effect is swamped by other uncertainties and random variables. Has anyone done the maths?

  26. Jeff said…”Theme to me is, mankind, all your arrogance stand aside, the solar system will show you your true place in the scheme of things”.

    ….Well said Jeff, What else is out there we haven’t even discovered yet, even just in our own solar system.

    What an incredible image, and what a place! Enceladus is very very special, at just the size of England you could drive across the thing in a day…and all this activity in such a small body! Those jets are coming from a nice “warm” place in the Tiger Stripes travelling at 2,100 km per hour. There’s liquid salty water slopping about at, and under the surface with possibly an entire ocean below the ice. No wonder Enceladus is a member of that exclusive club of moons with possible extratterestrial life.

    Long gone are the days when we thought sunlight was the only energy source for life, tidal heating vastly increases the places for possible organisms to exist.

    Was Earth right at the back of the queue when moons were being handed out? ;-) Of course we love Luna to death, but just think…!

  27. Faucher

    Enceladus reminds me of the old tv show Shadow Raiders.

  28. Steven Vallarsa

    “Message from Space”! That’s the name of that Japanese “Star Wars” movie from the late 70’s. Thank you Google! :)

  29. Thameron

    Wouldn’t that be full afterfreezer? Anyway lovely moon that Enceladus. Beautiful plumage.

  30. Chris Winter

    Shades of Stanley Schmidt’s novel Lifeboat Earth. ;-)

  31. daleks. DALEKS I Tell YOU!

  32. Pareidolius

    Shades of “Pushing Ice” by Alastair Reynolds . . . the moon that got away.

  33. Kryptonian

    Going cruisin’ in a spaceship, we’re so good at being bad
    We’ll destroy your little planet if you ever get us mad …

  34. JB of Brisbane

    @Anchor #24 – or how whenever an aircraft in a movie is in a power dive or death spiral, the accompanying sound effect is always that of the wind-driven siren of a Junkers Ju-87 Stuka dive bomber.

  35. Ethyachk

    Is anyone else reminded of the Invader Zim episode Battle of the Planets or is that just me?

  36. knobody

    my husband showed this picture to my 8 year old tonight. not only did he correctly name the moon and its planet, but he also told me that the “volcanos” were really water and the source of the E ring. science channel ftw.

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