Enceladus is erupting!

By Phil Plait | February 23, 2010 2:04 pm

On November 21, 2009, the Cassini spacecraft sliced past Saturn’s moon Enceladus, shaving the iceball at a distance of 1600 km (1000 miles). From that distance, the view was astonishing…

cassini_enceladus_nov091

It’s been known for some time that the south pole of Enceladus is lousy with geysers, erupting water into space (though the ultimate source of the water is still a bit of a mystery). But this new pass shows 30 geysers, 20 more than were previously seen! One major geyser also appears to have waned a bit since the last pass, showing that not only is stuff going on, but things are changing, too.

cassini_enceladus_nov092

This mosaic of the surface of Enceladus overlays a high-res optical image with thermal hot-spots. You can see that the hottest parts — which are actually at -90° C (-140° F), so I guess "hot" is in the (frozen) eye of the beholder — line up along a huge fracture in the moon’s surface. The fracture is called Baghdad Sulcus and is one of the places on the moon erupting water geysers. The fracture is about 500 meters (roughly 1/4 mile) deep, and this image shows about a 40 km (25 mile) swath along it. There’s evidence of particles from the geysers re-falling here, and also house-sized icy blocks that may be rubble that has been seismically shaken and settled downslope.

There’s a lot of science in those images, and in the others returned from that close pass. But I think my favorite from these is one that may also have scientific value, but, like almost everything Cassini sends back, is perhaps more striking for its artistry.

cassini_enceladus_nov093

That’s a crescent Enceladus, replete with geysers, and its parent planet Saturn in the foreground. Wow, that’s pretty. I love how gray Enceladus looks and how much brighter Saturn is. I was thrown for a moment; Enceladus has a reflectivity of nearly 100%, meaning it reflects nearly all the light hitting it, while Saturn only reflects 30-50% of the light that hits it (depending on how you measure it). But this depends on the viewing geometry! Enceladus is thin crescent, so the light is hitting it at a very low angle. A lot of the light hitting the moon is sent straight back toward the source (the Sun), so not much of that light gets sent off in other directions. It’s not that Enceladus is intrinsically fainter than Saturn, it’s just that the light is reflected off in another direction, and not towards Cassini in this image.

As in life, sometimes what you see depends on how you look.

Cassini has been orbiting Saturn since 2004, and in all that time it has not disappointed. It continues to return a veritable bounty of information about Saturn and its fleet of moons. If you want to stay on top of Cassini news, subscribe to the email list, and follow imaging team leader Carolyn Porco on Twitter!

CATEGORIZED UNDER: Astronomy, Pretty pictures
MORE ABOUT: Cassini, Enceladus, Saturn

Comments (33)

  1. Wayne Robinson

    “… It’s been known for some time that the south pole of Enceladus is lousy with geysers …”

    Enceladus is infested with lice? …

  2. Mike

    Moar missions! Moar space exploration! MOOAAAAAARRR!

    I can’t get enough of this stuff.

  3. DrFlimmer

    This looks like a fault line on earth, where the continents hit each other (or back away from each other like in the Atlantic ocean). That’s also where material from the interior “explosively” enters the exterior. Could be similar, but need not!

  4. Gary Ansorge

    So many pictures. So little time.

    Cool!

    GAry 7

  5. One also has to wonder what took them so long: A mosaic basically like the “new” one had been created by fans – and even turned into art within a few hours after the flyby.

  6. Douglas Troy

    That’s just too freak’in cool. I really enjoy pictures like this, because it brings into context the fact that our solar system is active, constantly changing and ever evolving.

  7. Ufo

    Beautiful. But I bet it’s Saturn in the background, not the foreground. Otherwise it would be quite a telescopic view.

  8. Jonathan

    Those close-ups sure look a lot like Europa.

  9. @#5 Dan Fischer: Well, it didn’t take us that long really… first off, the images were posted online almost as soon as they came down. The fact that amateurs were even able to put together some mosaics within hours of the downlink is a testament to that. The full set from the encounter was posted on the JPL site and a few select images were posted on the imaging team site, including half of that popular jets image shown at the top of Phil’s post. With those images on the ground, it is great that amateurs were able to put together some mosaics from the data so quickly, but don’t think that some of us, including myself, weren’t doing the same thing. However, for a press release like this on a big project like Cassini, coordination across instrument teams and the project leads is needed, as evidenced by our cooperation with the Composite Infrared Spectrometer team on this image release. This type of delicate cooperation and most importantly, data analysis isn’t done overnight, and takes time. Finally, remember that not everyone saw the amateur mosaics, and a major project press release like this can put this great dataset in front of more eyeballs.

  10. jest

    re: the first image.

    Welp, I know what my new laptop image background is…..

  11. Anne Verbiscer

    @#7 Ufo: Yep, you are correct. That is Saturn in the background, not the foreground.

  12. I love these images. Enceladus is just awesome. Kudos to the Cassini team! Awards and badges all around!!!

  13. John Paradox

    Is that Enceladus in your pocket, or are you glad to see me?

    J/P=?

  14. Clearly, these “geysers” you speak of are in fact the orbital maneuvering engines caught in the act of firing. NASA is hiding the truth, most likely in a hermetically sealed mayonnaise jar in Hangar 18.

  15. Messier Tidy Upper

    Awesome images and great write up. I love seeing & reading this! :-D

    Enceladus has a reflectivity of nearly 100%, meaning it reflects nearly all the light hitting it, while Saturn only reflects 30-50% of the light that hits it (depending on how you measure it).

    How does this compare with our Moon?

    I take it Enceladus is much more reflective and brighter – one of the brightest & most reflective in our solar system?

    How bright would Enceladus be if it were orbiting Earth insteadof our Moon?

    As in life, sometimes what you see depends on how you look.

    So very true.

  16. Pi-needles

    @ 15. Kuhnigget:

    Clearly, these “geysers” you speak of are in fact the orbital maneuvering engines caught in the act of firing. NASA is hiding the truth, most likely in a hermetically sealed mayonnaise jar in Hangar 18.

    No, no, its in area 52 – or was it area 53 or 51 or even area 25 instead? ;-)

    @ 9. Jason Perry: Here’s a very big THANKYOU from me to you and the rest of the Cassini team – you guys are awesome & continually show us us some truly wonderful breathtaking things. Your work is very much appreciated. :-)

    Must be great to do that for a living. I just wish I had your job! ;-)

  17. MadScientist

    That’s an unfortunate choice of words following “shaving” – NSFW! I’ll be imagining brass monkeys with razors now …

  18. Grand Lunar

    Might it be correct to coin the phrase “Enceladus: The new Io”?

    Beautiful!

  19. Grand Lunar

    @ Messier Tidy Upper

    “Enceladus has a reflectivity of nearly 100%, meaning it reflects nearly all the light hitting it, while Saturn only reflects 30-50% of the light that hits it (depending on how you measure it).

    How does this compare with our Moon?

    Our moon’s reflectivity varies from 6% at the darkest regions to 30% at the brightest regions.

    Can’t say how much brighter that would make Enceladus in our skies. I’m guessing brighter than Earth would appear from the moon.

    Of course, if Enceladus was orbiting Earth, I think it would melt.

  20. James Mayeau

    DrFlimmer Says:
    February 23rd, 2010 at 2:49 pm
    This looks like a fault line on earth, where the continents hit each other (or back away from each other like in the Atlantic ocean). That’s also where material from the interior “explosively” enters the exterior. Could be similar, but need not!

    How do you know that this is material from the interior?
    Previously Porco has said that the rotational tortion is not enough to maintain a liquid ocean core on a moon the size of enceladus. The information we need to solve this – is this geyser shooting out salt water – is withheld.

  21. James Mayeau

    So is it climate or the weather changing on Enceladus?

  22. There must be something in the water acting as antifreeze, and there would need to be an atmosphere, but even under pressure with the temperature being what it is it seems to me as if the water would freeze almost instantly. When will we be dropping a rover?

  23. Torbjörn Larsson, OM

    How do you know that this is material from the interior?
    Previously Porco has said that the rotational tortion is not enough to maintain a liquid ocean core on a moon the size of enceladus. The information we need to solve this – is this geyser shooting out salt water – is withheld.

    Even if the orbit input wouldn’t be enough in a static situation, there could be periods were orbital dynamics heat the moon to liquid reservoirs.

    But as a matter of fact, IIRC newer models shows how a liquid layer sustain prolonged heating.

    Is this geyser indicating liquid water? Theres two predictions here; 180 K is enough to sustain ammonia/water (partial) liquid formation as well as brines AFAIU. As a matter of fact, measurements of salts have been published. (Not withheld, why would they be, except in the minds of conspirationists – a conspiracy, always the least likely possibility of explanation by many orders of magnitude.)

  24. James Mayeau

    As a matter of fact, measurements of salts have been published. (Not withheld, why would they be, except in the minds of conspirationists – a conspiracy, always the least likely possibility of explanation by many orders of magnitude.)

    Read the link.

    Which is it?

    Beats me. I’m a violent star-explodey kind of guy, not an exooceanologist. I imagine the authors of the two papers have their opinions on both studies, and I’d love to hear what they have to say. I’d also like to see the spectra obtained by the no-salt-in-the-plumes team first (because a non-detection of something is always on shakier ground than a positive detection of something) before I would come to any conclusions.

    But thus is science. Two observations, two good teams, two very different conclusions. That’s what it’s like on the cutting edge… and we’ll need more observations to cut through all this. Happily, as Cassini orbits the Saturn system it will be passing directly through the plumes at least twice more, giving astronomers that many more chances to see what’s happening on that tiny little moon so far away.

    One chance down. They have had plenty of time to analyze the data, but still haven’t reported whether or not the plume is fresh water or salt.

  25. geeta

    Speculative deductions based on loads of assumption along with manipulations in each stage – from taking pictures to analyzing them and getting them published – just to keep the scientific profession from perishing and the to keep the grant flowing in. Soemthing that looks to earthly eyes as a geyser (in a picture whose accuracy is assumed) must be of water and so on and on…makes a nice fairytale. A result of having too many ‘working’ on too little real work; just as it is in other professions such as politics and business.

  26. Adam

    Mitch: High pressure will keep very cold water liquid. But I think the tidal forces of Saturn are thought to keep the core of the planet hot, which would help keep water liquid.

    That second image is striking to me in that the plumes are so big. They appear to be a thousand miles high or more. How fast must the ice particles be shooting out of those geysers to go so high, and even escape the moon!? I know some of the fall back down, but I’ve read that one of Saturn’s rings is formed by such particles.

    I’m also surprised that the geysers are visible in an image that was exposed for the moon itself. I didn’t think they had enough density to really be seen unaided. Or perhaps the image was made in a wavelength where the plumes are much brighter compared to the surface?

  27. D K

    @7 Saturn is in the foreground causing the shadow on Enceladus that was viewed as a cresent. If Saturn was in the background Enceladus would be fully lit and the cresent could not be seen from this viewpoint.

  28. bowdin deese

    When do they put some bacteria there? or some algae,and see if it flourishes…the first place humans put life outside of earth.

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