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The Dark Side of Iapetus

Posted by kdawson on from the like-e-ink-writ-large dept.

Hugh Pickens writes "The difference in coloring between Iapetus' leading and trailing hemispheres is striking. NASA's Jet Propulsion Labs has just released a report on a bizarre 'runaway' process that may explain the strange and dramatically two-toned appearance recently revealed in images collected during a close flyby by the Cassini spacecraft. Scientists believe that initially dark material on one side of Iapetus may have come from other moons orbiting Saturn in the opposite direction. Since Iapetus is locked in synchronous rotation about Saturn, as dusty material from the outer moons spiraled in and hit Iapetus head-on, the forward-facing side began to darken. As it absorbed more sunlight, its surface water evaporated, and vapor was transported from the dark side to the white side of Iapetus. Thermal segregation then proceeded in a runaway process as the dark side lost its surface ice and got darker still. Now the leading hemisphere is as dark as a tarred street and the trailing hemisphere resembles freshly fallen snow."

73 comments

  1. opposite direction moons by Harmonious+Botch · · Score: 1, Interesting

    "... other moons orbiting Saturn in the opposite direction."

    From what I recall of planetary formation, moons all came from an accretion disk, and should be all orbiting the same direction. I suspect that more likely the materials coating the dark side came from same-direction objects that were in eccentric orbits.

    1. Re:opposite direction moons by ajlitt · · Score: 1

      Isn't there a theory that has the Earth's moon being formed by a collision with a large object? Wouldn't a moon formed this way not be dependent on the path of an accretion disk?

    2. Re:opposite direction moons by Josef+Meixner · · Score: 4, Informative

      There are also moons which are considered to have been once independent objects caught by Saturns gravity. E.g. in this list the ones with a negative orbital period are retrograde. Saturn seems to have quite some of those.

    3. Re:opposite direction moons by stevesliva · · Score: 3, Interesting

      Wow, you're right to highlight the fact that they indicate retrograde satellites might be the cause. Iapetus itself is in an unusually inclined and distant prograde orbit... I hadn't heard any retrograde satellite theories for the dark region.

      --
      Who do you get to be an expert to tell you something's not obvious? The least insightful person you can find? -J Roberts
    4. Re:opposite direction moons by Harmonious+Botch · · Score: 1

      Theory once again gets crushed by facts. Thanks.

    5. Re:opposite direction moons by techno-vampire · · Score: 4, Informative

      Many of Saturn's moons are probably captured asteroids, and have highly eccentric orbits. For various reasons, it's a lot easier for a body to be captured into a retrograde orbit, going "the wrong way."

      --
      Good, inexpensive web hosting
    6. Re:opposite direction moons by rde · · Score: 4, Interesting

      It's a fairly substantial theory; you'd be hard-pressed to find any planetary scientist who thinks the moon formed any other way. The makeup of the moon (as it's currently understood) doesn't really accommodate alternate theories. As for its direction: when the Mars-sized planet whacked the nascent Earth, it most likely sent up an accretion disk of its own rather than a sending a huge chunk of proto-moon into orbit; this disk gradually formed the moon. Given that the disk's movement would be directed by the Earth, which would in turn be directed by the rest of the solar system, the moon's direction would, indirectly, be dictated by the solar system's original accretion disk. Pretty much the only reason (that I can think of, anyway) for a moon to have a retrograde orbit would be its capture as a more-or-less intact body.
      However, IANA[A-Z], so I'm willing to be contradicted on all this.

    7. Re:opposite direction moons by Anonymous Coward · · Score: 0

      Pretty much the only reason (that I can think of, anyway) for a moon to have a retrograde orbit would be its capture as a more-or-less intact body. Which is impossible since you would need a collision for any body to get trapped in a planetary gravity well. I think the only way to describe retrograde orbits is collisions with other Moons or interaction with a planetary atmosphere or proto-planetary gas cloud.
    8. Re:opposite direction moons by E++99 · · Score: 2, Interesting

      If you look at the gravity simulations of such a planetary collision, it seems that the orbit of the resulting moon is a product of the angle of impact more than anything else. So I my impression is that a retrograde orbit could be completely consistent with a moon that is the product of a collision.

    9. Re:opposite direction moons by Tablizer · · Score: 2, Interesting

      As for its direction: when the Mars-sized planet whacked the nascent Earth, it most likely sent up an accretion disk of its own rather than a sending a huge chunk of proto-moon into orbit; this disk gradually formed the moon. Given that the disk's movement would be directed by the Earth, which would in turn be directed by the rest of the solar system, the moon's direction would, indirectly, be dictated by the solar system's original accretion disk.

      But you couldn't change the orbital momentum of debris that easily that I can see. I see 3 general scenarios at the moment:

      1. The colliding object hit in the same direction that the proto-Earth was already rotating.

      2. The colliding object hit in the opposite direction of proto-Earth's rotation, but hit hard enough to reverse or angle the Earth's spin. But orbital pressure from nearby planets "corrected" it over time. Being at an angle may be sufficient, but being completely opposite may have hindered moon creation. It would be interesting to see such simulations.

      3. The colliding object hit in the opposite direction of proto-Earth's rotation, but because of the opposite direction of movement, the debri didn't orbit long and fell back to Earth due to tidal forces, leaving NO moon. But if this happened, then we wouldn't be talking about the moon. Thus, perhaps the collision was somewhat aligned with the existing rotation of the proto-Earth, otherwise we wouldn't be talking about the moon. (Perhaps there were other collisions that didn't generate moons because of this.)

      In short, the colliding object may have to be somewhat compatible with the existing rotation to create a moon, so a selection process reduces the chance of a counter-rotating moon forming via collision. Something that hits at the opposite direction of rotation generates more heat and less momentum than the other way around. Heat would just create debris clouds and plasma, which is not enough to form a moon. Collisions that "take advantage" of existing rotation will toss more debris into higher orbits.

      --
      Table-ized A.I.
    10. Re:opposite direction moons by malilo · · Score: 1

      There is an excellent book "What if the moon didn't exist" that actually details a ton of different scenarios for how the earth + rocky body collision could have been different (larger, smaller, different directions) resulting in all kinds of different outcomes (relies heavily on evolutionary theory - for instance, without tidal slowing of the earth's rotation, day's would be 4 hours long and animal life would certainly be adapted differently). Anyway, I recall the first chapter detailed the prevailing theory of the collision, and it definitely hit counter to the earth's rotation which was supposedly 4 hours/day and slower afterwards.

      --
      "sometimes he felt that his whole life was a dream, and he wondered whose it was and whether they were enjoying it."
    11. Re:opposite direction moons by MBGMorden · · Score: 1

      There is also a television program (a bit older now - narrated by Patrick Stewart) called "What if we had no moon?" that deals with the same topic. It's available on DVD from the Discovery Channel's online store.

      One of the key points it touched on, aside from the length of the day, was just how much the moon serves the stablize our planet's "wobble factor". While planets like Mars for example, tend to wobble all over the place as they orbit, Earth tends to be more stable as the moon acts as a gravitational anchor. This means that most areas are relatively the same temperature from year to year. Without it, we could have arctic conditions in one region one year and the next it would be extremely hot (I would say tropical but that implies vegetation, and there likely would be little or none).

      So essentially, for us to find a random habitable planet, we need a rocky planet, about our size, that has a Sun roughly our size, spaced at a similar distance, with an abundance of water, and and it needs to have suffered an impact early in it's life by a large body of just the right size and just the right angle to form a relatively large moon to stabilize it as it orbits. It then either must have an oxygen rich atmosphere to begin with, or it needs some other atmosphere rich in some molecule containing oxygen atoms (such as CO2), and enough chemicals to produce a life form that will use that and output Oxygen as a byproduct.

      Now, all that did happen at least once. We're standing on the result. I have no idea how common it is, but my guess is not very. That's not to say that life itself isn't common on other planets, but unlike on sci-fi shows, finding an existing, habitable, Earth-like planet, requiring no terraforming, just out there, would seem to be INCREDIBILY rare. Now, the sheer size of the universe to me, says that it must have happened more than once. There's just too many galaxies and star systems out there for it to not have. But, if they odds are high enough, we might very well be in a situation where an Earth-like planets occurs, in say, 1 out of every 10 galaxies. Now thats just a completely made up number, but it's not out of the realm of possibility. If that's the case, then I sincerely doubt, regardless of ANY technological advances made by ourselves or any other advanced civilization, that humans would EVER come across one of those, even if they did exist.

      --
      "People who think they know everything are very annoying to those of us who do."-Mark Twain
    12. Re:opposite direction moons by FLJerseyBoy · · Score: 1

      The book (out of print, published 1993) is currently available on Amazon for as little as a penny. Looks very cool (as do some of the other books which Amazon mentions on the same page, like the one called The Big Splat, or How Our Moon Came to Be.

      Thanks for the recommendation.

    13. Re:opposite direction moons by Convector · · Score: 1

      It is by far the best accepted theory, although I seem to recall that a few details that haven't been worked. The isotope ratios are a mystery; both the Earth's mantle and the Moon have identical oxygen and silicon ratios are identical. If the impactor had a different source than the Earth, it's hard to explain this unless the two bodies underwent complete mixing, and that's not predicted by the dynamical models. IAAPSBNAGCATIPMAA (I am a Planetary Scientist, but not a Geochemist, and this isn't precisely my area anyway), so this issue may have been resolved without my knowing about it.


      Good references in general are:

      • Asphaug, E., C. B. Agnor, and Q. Williams, Hit-and-run planetary collisions, Nature 439, 155-160, (2006) doi:10.1038/nature04311
      • Canup, R. M., Dynamics of lunar formation, Annu. Rev. Astron. Astrophys. 42, 441-475 (2004).
      • Canup, R. and E. Asphaug, E., Origin of the Moon in a giant impact near the end of the Earth's formation, Nature 412, 708-712 (2001).
      • Origin of the Earth and Moon, eds Canup, R. & Righter, K., Univ. Arizona Press, Tucson, 2000.
      • Stevenson, D. J., Origin of the moon -- The collision hypothesis, Annu. Rev. Earth Planet. Sci. 15, 271-315 (1987).
    14. Re:opposite direction moons by CorSci81 · · Score: 1

      One of my office mates in grad school actually worked on this very problem. What I recall of his preliminary research was that one potential (but unlikely) explanation was the impactor maybe had formed along-side the Earth. However, isotope distributions among the terrestrial planets appeared to be completely random from dynamical models of accretion. While there may be some segregation in the protoplanetary disk there are a sufficient number of large accretion events from bodies from all over the inner solar system that the end result is somewhat a game of chance.

      What I remember of Canup's models is that the iron core of the protoplanet ends up merging with Earth and the Moon ended up being formed largely out of the impactor's mantle material and a little bit of Earth's. But her original dynamical model predicted insufficient mixing to account for the homogeneity in isotopes. Right before I left he and Stevenson began exploring transport in the silicone vapor atmosphere that would've enveloped both the Earth and accretion disk shortly after the impact, but I'm not sure if they ever got it to work out. Some other grad students actually began work on a smooth particle hydrodynamical model to expand on Canup's at that point too, but no idea where that's at either (this was in early 2006).

    15. Re:opposite direction moons by Tablizer · · Score: 1

      without tidal slowing of the earth's rotation, day's would be 4 hours long

      I am curious how they know this because the collision itself may have added or subtracted rotation. Mars has no significant moon, and yet it has about the same period as the Earth.

      --
      Table-ized A.I.
    16. Re:opposite direction moons by aqk · · Score: 1

      Check out Phobos and Deimos.

      --

      .
      - aqk
      F U /. illiterates.
  2. There is no dark side of Iapetus by ajlitt · · Score: 4, Funny

    As a matter of fact it's all dark.

    1. Re:There is no dark side of Iapetus by Anonymous Coward · · Score: 0

      dur...THUMP.....dur.....THUMP......dur.....THUMP......

  3. Goth Chicks by Anonymous Coward · · Score: 0

    The Dark Side of Iapetus is on MySpace, if you want to count her as a friend.

    1. Re:Goth Chicks by fractoid · · Score: 2, Funny

      The Dark Side of Ur Anu... wait, no, too easy. *resumes lurking*

      --
      Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
  4. what by User+956 · · Score: 1

    Scientists believe that initially dark material on one side of Iapetus may have come from other moons orbiting Saturn in the opposite direction ... As it absorbed more sunlight, its surface water evaporated, and vapor was transported from the dark side to the white side of Iapetus.

    that's not a scientifically-described result of synchronous rotation. That's apartheid.

    --
    The theory of relativity doesn't work right in Arkansas.
  5. Pink Floyd got it right by Corpuscavernosa · · Score: 2, Funny

    "I'll meet you on the Dark Side of Iapetus" just doesn't have the same flow...

    --
    We figured out a long time ago that it's easier to elect seven judges than to elect 132 legislators.
    1. Re:Pink Floyd got it right by TapeCutter · · Score: 1

      "I'll meet you on the Dark Side of Iapetus"

      I belive the word is "see" rather than "meet", also there is nothing in the lyrics that states what moon they were talking about. /pedant

      --
      And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
    2. Re:Pink Floyd got it right by jamesh · · Score: 1

      When someone around these parts speaks of 'the Moon', it's normally pretty clear which moon they are talking about.

    3. Re:Pink Floyd got it right by arbitraryaardvark · · Score: 1

      obligatory Eddie and the Cruisers

      The dark side's callin' now, nothin' is real
      She'll never know just how I feel
      From out of the shadows she walks like a dream
      Makes me feel crazy, makes me feel so mean

      Ain't nothin' gonna save you from a love that's blind
      When you slip to the dark side you cross that line
      On the dark side, oh yeah
      On the dark side, oh yeah

    4. Re:Pink Floyd got it right by dunkelfalke · · Score: 1

      that's no moon... it's a space station!

      --
      "It's such a fine line between stupid and clever" -- David St. Hubbins, Spinal Tap
    5. Re:Pink Floyd got it right by TapeCutter · · Score: 1

      Absolutely, but that doesn't mean I'm wrong. /pedant

      --
      And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
    6. Re:Pink Floyd got it right by laejoh · · Score: 1

      I find your lack of original conversation disturbing.

      ;-

  6. Monolith... by Anonymous Coward · · Score: 0

    ... of course.

    (That business about Jupiter in the movie was just to throw off the public while the real expedition went to Saturn. And you're right. They DID fake the moon landings in a studio. But they still spend the money on a spaceship...)

  7. Segregate by 'Hotness'? by rts008 · · Score: 0, Offtopic

    I nominate Natalie Portman in Hot Grits as a baseline for this study....

    "Thermal segregation then proceeded in a runaway process as the dark side lost its surface ice and got darker still. Now the leading hemisphere is as dark as a tarred street and the trailing hemisphere resembles freshly fallen snow."

    So, we can terraform hot planets by tarring the streets and thus creating freshly fallen snow?...or does this mean that if we tar the streets then Natalie Portman will sled away with me in the new snow?

    Do we have to create the streets first?, or just start 'tarring' everything- tarred and feathered?...would this be better still? The tar and nicotine content of my smokes must be interfering here....I'm going back to smoking hot grits....be back to you all after the study is completed next year...decade...century...whatever.( If Natalie Portman is involved, then don't expect to hear from me at all- I'll probably die from shock and not be able to reply!!!)

    --
    Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
  8. Obi Wan by mihamed · · Score: 0

    That's no moon!

    1. Re:Obi Wan by tylersoze · · Score: 2, Insightful

      Actually you must be thinking of Mimas: http://en.wikipedia.org/wiki/Mimas_(moon)

    2. Re:Obi Wan by hazem · · Score: 1

      It's more like one of those balls of flour and sugar coated in powdered sugar - but only with a dash of cocoa on it.

      Hmmm... giant space pastries!

    3. Re:Obi Wan by mihamed · · Score: 1

      Indeed so. But Iapetus with its' two-tone appearance resembles the second (unfinished) death star. :)
      http://en.wikipedia.org/wiki/Image:DeathStar2.jpg

    4. Re:Obi Wan by RuBLed · · Score: 1

      Plus that wide crater with a suspicious black dot on the center.. a dead giveaway.. on further thought, where is that thing pointed?

    5. Re:Obi Wan by daeley · · Score: 1

      on further thought, where is that thing pointed?

      Well, you know the Asteroid Belt...

      --
      I watched C-beams glitter in the dark near the Tannhauser gate.
  9. rotten moon by Anonymous Coward · · Score: 0

    kinda reminds me of this http://plantpathology.tamu.edu/Texlab/Fruit/citrus/bups/citrus28.JPG

  10. 2001 by Matti-han · · Score: 0, Redundant

    But where's the Monolith?

  11. Here's another thought by NotmyNick · · Score: 1

    Perhaps these moons, which do orbit retrograde, are captured objects?

    --
    Notmysig
  12. He's heading towards that small moon by adamkennedy · · Score: 2, Interesting

    obiwan> That's no moon...

    http://saturn.jpl.nasa.gov/multimedia/images/image-details.cfm?imageID=2763

    1. Re:He's heading towards that small moon by Anonymous Coward · · Score: 0

      obiwan> That's no moon...


      Our moon rings like a bell when struck (as if hollow), has unusually large concentrations of titanium and beryllium, has a strangely high surface radioactivity, localised concentrations of high mass below the surface with noticeable gravity effects, its minerals are far older than earth's ...

      Is it the ship that brought life here?
  13. A really strange moon in multiple ways by Tablizer · · Score: 5, Interesting

    Some other mysteries are coming together. There are more data on the signature mountain ridge that gives Iapetus its "walnut" appearance. In some places it appears subdued. One big question that remains is why it does not go all the way around...And the ridge looks too solid and competent to be the result of an equatorial ring around the moon collapsing onto its surface. The ring theory cannot explain features that look like tectonic structures in the new high resolution images.

    So the collapsed ring theory (posted earlier on /.) is falling out of favor? So the walnut mystery remains. Giant impacts can sometimes mess up a moon's shape, but usually the odd damage is on the opposite side of the impact, not a circumference ring ridge. Whoever can pose a physical scenario that can cause such a feature (outside of orbiting ring collapse) may somebody have it named after them.

    --
    Table-ized A.I.
    1. Re:A really strange moon in multiple ways by Anonymous Coward · · Score: 0

      It's just poor injection moulding.

    2. Re:A really strange moon in multiple ways by Anonymous Coward · · Score: 0

      Perhaps the hot/cold effect created the ridge at some early point when Iapateus was more plastic. If the axis was tilted differently, the ridge could represent the hot/cold boundary.

    3. Re:A really strange moon in multiple ways by volcanopele · · Score: 1

      The ridge is looking more and more like a tectonic structure. If you have red-blue 3D glasses, you can look at the topography around the western end of the "ridge": http://photojournal.jpl.nasa.gov/catalog/PIA08379 In this area, the ridge is not continuous, but is broken up into a series of mountains. These mountains resemble mountains seen elsewhere in the solar system that are formed from thrust faulting, again suggesting that this feature is tectonic, rather than something depositional, as per the ring theory. Another issue with the ring theory is that the ridge appears to be a competent structure, a feature with some strength to it. A ridge made up of deposited ring particles would likely have slopes near the angle of repose [the angle of slopes formed by loose material under the force of gravity], whereas many parts of the ridge have slopes greater than the angle of repose.

      --
      The Gish Bar Times - Blog covering Jupiter's moon Io
    4. Re:A really strange moon in multiple ways by Tablizer · · Score: 1

      The ridge is looking more and more like a tectonic structure.

      Perhaps, but nobody has proposed any realistic scenario with it that would produce such a ring. My hat-ass guess would be that it used to have a much faster rotational spin that induced volcanism at the equatorial bulge, perhaps with the help of a now-gone partner producing tidal effects. It would be interesting to see a simulation of the damage caused by such close and spinning bodies.

      --
      Table-ized A.I.
  14. Diesel by flyingfsck · · Score: 1

    Well, evidently, the other moons are diesel powered and Lapetus is flying into the smoke trail - cough, cough...

    --
    Excuse me, but please get off my Pennisetum Clandestinum, eh!
    1. Re:Diesel by Anonymous Coward · · Score: 0

      Nothing like a good old american diesel engine without a particulate filter and running on high sulphur diesel fuel.

  15. It's full of... by Anonymous Coward · · Score: 0

    Water vapor? Well thats a let down.

  16. Mod up! by EvanED · · Score: 1

    You so deserve both funny mods and karma for that

  17. Forget a "bizzare runaway process"... by NPN_Transistor · · Score: 2, Funny

    Everyone knows that Iapetus is dark on one side to indicate the presence of a large black monolith.

    1. Re:Forget a "bizzare runaway process"... by MichaelSmith · · Score: 1

      Everyone knows that Iapetus is dark on one side to indicate the presence of a large black monolith.

      If we send Cassini down to investigate I doubt it will have the intelligence to blurt out that final message.

      --
      http://michaelsmith.id.au
  18. O Qua Tangin Wan by Anonymous Coward · · Score: 0

    That's no moon!

  19. @rts008 by hyades1 · · Score: 0

    I have to agree that rts008's comment on Natalie Portman in Hot Grits is off topic. If some link can be found between "Natalie Portman" and "moon", however, that's an entirely different issue. One worth contemplating. At length.

    --
    I've calculated my velocity with such exquisite precision that I have no idea where I am.
  20. wtf? by sergiolopes · · Score: 2, Informative

    From TFA: "230 degrees Fahrenheit or 127 Kelvin"

    Not even NASA gets this right???

    1. Re:wtf? by Anonymous Coward · · Score: 0

      From TFA: "230 degrees Fahrenheit or 127 Kelvin"

      Not even NASA gets this right??? It's just you who doesn't get it right. From TFA: "minus 230 degrees Fahrenheit or 127 Kelvin". Unless your point is that it should have rounded to 128 Kelvin?
    2. Re:wtf? by sergiolopes · · Score: 1

      Ok, my bad. I'm just not used to seeing "minus" written all out instead of the proper minus sign (-).

  21. symbols of eastern thought... by Anonymous Coward · · Score: 0

    So its a giant planetary yin-yang? Or do we need to terraform some contrasting dots to make it more recognizable?

    And back to the diesel comment... We need to get those other moons some cleaner burning biodiesel ;)

  22. Dark side, eh? by DeusExCalamus · · Score: 1

    Is this when ITapetus blinks, then? ....I'll get my spacesuit.

    --
    "...Sleep comes like a drug in God's country Sad eyes, crooked crosses in God's country..."
    1. Re:Dark side, eh? by DeusExCalamus · · Score: 1

      *Iapetus, rather....

      --
      "...Sleep comes like a drug in God's country Sad eyes, crooked crosses in God's country..."
  23. 2001 References?? by oni · · Score: 3, Insightful

    No references to the book 2001, A Space Odyssey yet? You guys are slipping. In the mid '60s, when A.C. Clarke wrote the book, he asked asked astronomers (mainstream scientists, not UFO nuts) "if you had to pick one object in the solar system that appeared artificial, what would it be?" They all picked Iapetus. At the time, the blurry photos we had from ground-based telescopes could tell us that it was 50% light and 50% dark, but nothing else. It was a big mystery, even after the Voyager flybys. For that reason, Clarke used Iapetus as the sight of the monolith stargate (the movie version used Jupiter).

    We're really lucky to live in a time when all these mysteries are solved.

    1. Re:2001 References?? by Teancum · · Score: 2, Interesting

      While that may be solved, the equatorial ridge on Iapetus is just as confounding, perhaps even more so.

      Crazy individuals like Richard Hogland are suggesting things like it is a large spacecraft aka Death Star due to this and other physical structures on this satellite of Saturn, but even from a pure geological/scientific viewpoint there are many more questions to be asked about this than have been answered.

      It will be interesting to see if any follow-up mission to Saturn will ever happen after the Cassini mission ends within my lifetime, as there certainly have been some very amazing discoveries that deserve a strong follow-up investigation. It is amazing now that we have discovered such an amazing variety of worlds to explore even within our own Solar System, which is now beginning to help us to explain this hunk of rock that we live on right now as well.

      Or more specifically, when you try to do a statistical comparison with a sample size of one, you tend to have all kinds of wild and crazy theories that get thrown around using that data point. Now that we have nearly 100 different worlds to compare the Earth to in terms of geological formation, structures, hydrology, and weather patterns; we certainly can start to make some much more informed guesses about what is happening right now here and what we can expect in the future.

    2. Re:2001 References?? by Anonymous Coward · · Score: 0

      http://science.slashdot.org/comments.pl?sid=321903&cid=20908673 Bit late...This guy snuck one in a few hours ago :)

    3. Re:2001 References?? by UbuntuDupe · · Score: 1

      Jupiter ... Jupiter ... oh yeah, "and beyond the infinite".

      That was the point in the movie's script where the writers said, "hey, I think we did a great job so far. Just scribble something down for the rest and we'll call it day."

      --
      Apology to Ubuntu forum.
    4. Re:2001 References?? by oni · · Score: 1

      It will be interesting to see if any follow-up mission to Saturn will ever happen

      I think it's unlikely to happen for 50 years or more, and that's kind of sad.

      But who knows, maybe there'll be some major technological advance that'll make Cassini-like probes common place. Maybe we'll build a space elevator, or maybe we'll start using nerva rockets. Heck, if we (the US) can manage to get Ares built, think of the upper stage booster we could mount on that puppy! We could have landers the mass of Cassini - maybe.

      In the mean time, we can get excited about New Horizons (what I've been trying to do is get my nephew to understand the concept that, no matter how hard he wishes for it, he can't possibly know what Pluto looks like, and no human has ever seen it - that way, when the pics come in, it will be something special for him). And if the Jupiter Icy Moons Orbiter mission happens, that'll be awesome too.

    5. Re:2001 References?? by Teancum · · Score: 1

      It is too bad that New Horizons can't get to Saturn in a "grand tour" arrangement with Pluto, but I do understand that such situations are rather unusual. The Voyager opportunity was rather unusual in terms of how the planets seemed to line up for a perfect low delta-v opportunity to visit all of them. I'm not sure how hard a Jupiter-Saturn-Pluto arrangement would be, but I can't imagine it happens that often either... I'm not ready to do the math to predict the resonance of those three bodies at the moment. An Earth-Jupiter-Pluto arrangement happens a bit more often, and that I do understand.

      Even so, it is seemingly common now for probes to get to Jupiter, where a visit like New Horizons getting to the Jovian system is not only not front page news, I'm not even sure it got into my hometown newspaper or made it onto the television news. This is good for science in general, as scientists can get their job done now to study these objects without becoming rock stars like Carl Sagan. (multiple meanings of that term, BTW) Unfortunately it is also jading the public and congress that missions like this have been done and all of the science that is needed for space exploration has been done. Senator Proxmire's legacy at attacking NASA and being highly critical of its funding is finally starting to pay off, unfortunately.

  24. Phoebe is retrograde by EccentricAnomaly · · Score: 1

    Phoebe was a leading contender as a source for the material for years (although it has recently been ruled out). And it is in a retrograde orbit.

    When a moon is far away from the central body, retrograde orbits are stable, and prograde orbits aren't. Pretty much every gas giant has retrograde moons far out.

    These moons likely escape and are captured over long period of times. They are probably the same population as the centaur asteroids near Saturn. To know for sure, we need to figure out the composition of these moons and compare them to the composition of the centaurs.

    --
    There are 10 types of people in this world, those who can count in binary and those who can't.
  25. Let That Be Your Last Battlefield by kidcharles · · Score: 2

    I'll bet you these guys are from Iapetus.

    --
    Ceci n'est pas une sig.
  26. Black on White or White on Black? by Convector · · Score: 2

    This picture shows a bright field with dark material down in the craters. That suggests to me that the impacts excavated a bright veneer to uncover dark material beneath, which is at odds with the image caption and the idea that the dark material is debris from other satellites. But I guess that's why I'm not a surfaces person.

  27. Obligatory Bad Car Analogy by PPH · · Score: 2

    Its like millions of years of bug splats on your windshield.

    --
    Have gnu, will travel.
  28. Re:A really strange moon in multiple ways (ellipti by Tablizer · · Score: 1

    ...faster rotational spin that induced volcanism at the equatorial bulge, perhaps with the help of a now-gone partner producing tidal effects.

    Now that I think about it, if the orbit with the parter was highly elliptical, then the tidal friction could get pretty strong. It would pull and then push repeatedly for each orbit. Io IIRC is heated more due to ellipticity (although it has no co-moon near it).

    Done! Where's my Nobel? ...What?...Evidence? Simulation? Math? Naw, that's for the little people :-)

    --
    Table-ized A.I.