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The Strangest Moon In the Solar System 141

StartsWithABang writes Moons in our Solar System — at least the ones that formed along with the planets — all revolve counterclockwise around their planetary parents, with roughly uniform surfaces orbiting in the same plane as their other moons and rings. Yet one of Saturn's moon's, Iapetus, is unique, with a giant equatorial ridge, an orbital plane that doesn't line up, and one half that's five times brighter than the other. While the first two are still mysteries, the last one has finally been solved.
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The Strangest Moon In the Solar System

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  • Medium. (Score:5, Informative)

    by Anonymous Coward on Thursday February 05, 2015 @06:42AM (#48987453)

    Linking to Medium is the new linking to LiveJournal.

    • Re:Medium. (Score:5, Insightful)

      by TWX ( 665546 ) on Thursday February 05, 2015 @10:50AM (#48988519)
      I guess the people that used to read Time Magazine and Readers' Digest are the new target audience of Slashdot.

      After all, we could have links to scientific papers or at least their abstracts written by actual scientists who studied the phenomena.
      • TL;DR

        Besides, it's PICTURES!

        • by ncc74656 ( 45571 ) *

          Besides, it's PICTURES!

          ...and text 2-3x larger than it needs to be. Had to press Ctrl-- a few times to get it back down to roughly what every other website uses. Are they writing for the semi-blind?

    • Re: (Score:2, Informative)

      by Anonymous Coward

      How appropriate that this is the Starts with a Bang blog: way too many sentences in the postings on this site end with a bang.

      ... one half of Iapetus is only about one-fifth as bright as the other!

      But one of them has!

      ... density of about seven dust-sized grains per cubic kilometer!

      ... and finally know why it has a yin-yang coloration unlike anything else!

      Zowie! Boom! Kablooie!

      These articles read like a comic book. When I'm looking for scientific details, the style of these articles is really offputting.

      • by Anonymous Coward

        Yet another reason to put a tax on the exclamation point.

  • Counterclockwise? (Score:1, Insightful)

    by Anonymous Coward

    Viewed from which side? Counterclockwise does not apply here.

    • Re: (Score:3, Informative)

      by Keramos ( 1263560 )

      Viewed from which side? Counterclockwise does not apply here.

      Viewed when looking down from the north pole. This is mentioned in TFA, per

      Rather that [sic] (looking down from the north pole) orbiting counterclockwise around its parent planet, which all the other moons do, Phoebe revolves clockwise around Saturn.

      • by Anonymous Coward

        But which way is north?

        • by Anonymous Coward

          But which way is north?

          Up

          • This is all very northern-hemisphere-centric reasoning. Some day South Africa will be running the show, and you can bet that the moon will revolve clockwise.
        • I was going to say that since all planets (and most moons) with the exception of Uranus have their rotational axis all lined approximately the same way as Earth, that the north pole could be defined as the same as earth: the pole from which the planet seems to be rotating counter-clockwise (or anti-clockwise for you Brits).

          But there's a glaring exception to that rule: Venus rotates in the opposite direction - clockwise from its "northern" pole. The leading theory is, like Earth, Venus was struck by a
          • The angular momentum imparted by the planetoid caused Venus to "flip".

            Wouldn't it keep rotating? Why would it flip end-to-end and then stop?

            • Same thing that keeps a gyroscope standing on end - conservation of angular momentum. Once an external force stops pushing one end of a gyroscope (or a colliding body hits Venus but is just about completely absorbed by it), the gyroscope stabilizes - albeit with a bit an precession (as mentioned in an earlier post about the precession of Earth's north pole).
        • Re:Counterclockwise? (Score:5, Informative)

          by rubycodez ( 864176 ) on Thursday February 05, 2015 @12:30PM (#48989637)

          Towards Polaris, and in fact that gives the direction of "galactic north" too. Note due to precession of Earth's axis after 3000 AD Gamma Cephei will become the pole star, and Iota Cephei in 5200 AD. Thuban was the pole star in 3000 B.C. Polaris will again become the pole star about 27,800AD

    • Viewed from which side? Counterclockwise does not apply here.

      Almost planets and their moons orbit in, or closely aligned to a single plane (the ecliptic). Looking "down" (from the North) on a tangent to that plane, the planets and satellites will be seen to be rotating clockwise as most of their axes are also more or less perpendicular to that plane.

    • Re:Counterclockwise? (Score:4, Informative)

      by tylersoze ( 789256 ) on Thursday February 05, 2015 @10:44AM (#48988451)

      Or just use the right hand rule :) Where "north" is by definition the positive direction of the total angular momentum pseudo-vector of the solar system.

  • by Anonymous Coward

    Every single hash-laden cloudfront link is a tracker. No thanks, Medium.

  • by Eunuchswear ( 210685 ) on Thursday February 05, 2015 @06:51AM (#48987487) Journal

    It's HUGE.

    • It's not a moon so it doesn't count.

      • Our moon is not a moon? Sorry?

        (BTW I know that there are bigger moons than ours, but they're moons of Jupiter FFS).

        • by Anonymous Coward

          It was a Star Wars IV reference/joke.

        • by Sique ( 173459 )
          Actually, Saturn also has a moon that is larger than Earth's Moon, Titan. Albeit the largest moon of Neptune, Triton, misses the size of Earth's Moon by about 200 km of radius.
        • Our moon is not a moon? Sorry? ...

          The Earth's "moon" is not a moon, the Earth-Moon system is a double planet. At no point does the Moon's orbit actually curve away from the Sun, it always curves toward the Sun. As it goes on the "inside" of the orbit it flattens out, but does not curve away from the Sun.

          In other words, the moon is influenced more by the Sun's gravity, than the Earth's gravity.

    • I'm not sure why you're modded funny. The relative sizes of the Earth/Moon system is a total anomaly, so much so that it is very very close to the point where you have to call them a double planet rather than a planet and moon.

      • by Eunuchswear ( 210685 ) on Thursday February 05, 2015 @10:41AM (#48988423) Journal

        There is also the bizzare coincidence that the size of our moon, viewed from the earth is almost exactlty the same as the sun, viewed from the earth -- hence total eclipses of the sun.

        • Re: (Score:2, Insightful)

          by Anonymous Coward

          The moon has been receding from the earth since its creation. The coincidence is that we are here to observe the moon during the time when the visual sizes are so similar.

          • Coincidence eh? Or is it that God wanted us to explore our world...

            "The Moon is unique in the solar system in its large relative size compared with the Earth. The Moon appears from the Earth to be the same size as the sun, in perfect artistic symmetry, unlike any known other planet-moon system. [...] To many Christians, these characteristics appear as "clues" or "hints" left by God for men to discover. [...] The Moon appears to have the same size as the Sun when viewed from Earth. This creates a unique symm

            • The problem with those events with a small probability is that there are so many of them that a few will always occur. It's like saying that god is responsible for the lottery winner because the probability of each player is very low.

            • There is a possibility a large moon is necessary for intelligent life, or at the least the strong tides (really huge at the beginning) were helpful in stirring things up for the appearance of dumb life.

              • There is a possibility a large moon is necessary for intelligent life,

                It's a possibility. It attracts a fair amount of discussion. With a sample size of 1, we have no way of assessing whether or not it's a true statement. It is just as likely that the development of life, and intelligence, are completely unrelated to the presence of a medium-size moon.

        • by dave420 ( 699308 )
          That's only temporary. The moon is receding, and so the total eclipses won't last forever.
      • The relative sizes of the Earth/Moon system is a total anomaly,

        Is it? Moon diameter is 0.2724 that of Earth ; Charon's diameter is 0.5050 that of Pluto. For masses the corresponding ratios are 0.0122 (1/81) and 0.1160 (1/9). so, is the Moon a "total anomaly"?

        so much so that it is very very close to the point where you have to call them a double planet rather than a planet and moon.

        I've been taking an interest in astronomy for 40 odd years now, and I don't know what the point where I'd "have to" call a syste

    • That's no moon; that's half a binary planet.

    • by houghi ( 78078 )

      obb: I don't think that's a moon.

  • Unique? (Score:5, Insightful)

    by stjobe ( 78285 ) on Thursday February 05, 2015 @06:54AM (#48987501) Homepage

    Yet one of Saturn's moon's, Iapetus, is unique

    Aren't they all unique?

    • Re:Unique? (Score:5, Funny)

      by Keramos ( 1263560 ) on Thursday February 05, 2015 @07:03AM (#48987527)

      Yet one of Saturn's moon's, Iapetus, is unique

      Aren't they all unique?

      Yes, and they're all special too.
      And they can grow up to be any kind of planet they want.

      AS LONG AS IT'S A DWARF PLANET, RIGHT PLUTO? HA HA HA, LOSER!

      • But our work isn't finished. Now that we've gotten Pluto kicked off the list of planets, we need to get fucking Plutonium off the Periodic Tale of Elements.
        • I'm happy to compromise and leave plutonium there, as long as elements 119 and 120 aren't named Mickium and Donaldium. Although perhaps given the length of certain copyrights, those names might be appropriate if they happen to fall into the island of stability.
    • by Anonymous Coward

      No, only Iapetus is unique. All the other moons are the same, but Iapetus isn't. That's the one thing that makes it different from the rest.

  • To summarize. (Score:2, Informative)

    by jellomizer ( 103300 )

    I found this article to be rather long winded in order to create a story with suspense.
    The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.

    Done, saved you a long and pointless naritive.

    • by Anonymous Coward

      in order to create a story with suspense

      Wikipedia: [Cassini] correctly deduced that Iapetus is locked in synchronous rotation about Saturn and that one side of Iapetus is darker than the other
      Medium: Iapetus, presented a tremendous mystery to Cassini.

    • Re:To summarize. (Score:5, Informative)

      by Keramos ( 1263560 ) on Thursday February 05, 2015 @08:16AM (#48987713)

      I found this article to be rather long winded in order to create a story with suspense. The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.

      Done, saved you a long and pointless naritive.

      Actually, that's not quite correct. You've got two errors there, and missing the real mystery, although the article itself actually fails to explicitly specify what the solution is.

      The darker side is actually the leading hemisphere, not the far or outer side (from Saturn). Dust doesn't onto the far side, the moon plows through it in places, getting dust on the leading side. No mystery here for quite a while though - telescopes have been able to make out "the dark patterns look a lot like dust" for quite a while. The Phoebe ring itself was only detected about 10 years ago, but it was expected that dust was coming from the outer moons for a while.

      The thing is, if the only process happening was that dust was being swept up by Iapetus, then every time the dark side faced the Sun, the dark coating would heat up, cause the ice underneath it to sublime (think evaporate, if that doesn't mean anything - it's close enough) and freeze again over the dust, leaving behind a light surface again. But we see a dark surface. Why? Mystery!

      The solution (which the article doesn't really explain fully) is that initially dust from the ring caused ice to turn to gas, leaving behind a dark residue that we now see (and the Cassini probe has been able to measure), but instead of just floating around above the (relatively) warm, dark surface until it faces away from the Sun and cools down, much of the vapour refreezes on the light side as it passes over it due to the lower temperature there.

      The dark residue (not the original dust) now causes further heating each orbit, repeating the cycle. Over time, a large amount of ice from the leading side is being evaporated away, leaving that side to get darker and darker from the residue, with a certain amount of the ice migrating to the light side and refreezing (as light coloured ice) keeping it nice and bright.

      TLDR: Mystery! Dust doesn't explain the dark leading side of Iapetus! Ice would cover it in a shiny coat each orbit. Planetary detectives trace the culprit to dark residues left behind as heated ice moves to a new neighbourhood on the cooler side of the moon. More dark areas means more solar heating, and more ice migrating away in a self-perpetuating cycle. Mystery solved! Good job, planetary scientists!

      • This!
        By all means ignore the GP post and RTFA. Lots of cool pictures and chat about how Phoebe is special and how ridges from old impact craters on Iapetus are really old.

        Unless you're not all that into space stuff... then I'd understand if you might find TFA "long-winded" and would probably appreciate having more time for reading buzzfeed "articles".

      • The one thing that I'd add is that the identification if the dark material on Iapetus as debris from the Pheobe ring was news in 2007.
      • by DRJlaw ( 946416 )

        Planetary detectives trace the culprit to dark residues left behind as heated ice moves to a new neighbourhood on the cooler side of the moon. More dark areas means more solar heating, and more ice migrating away in a self-perpetuating cycle. Mystery solved! Good job, planetary scientists!

        Interplanetary redlining and white flight! Bad job, scientists!

    • by NoNonAlphaCharsHere ( 2201864 ) on Thursday February 05, 2015 @08:23AM (#48987721)

      Done, saved you a long and pointless narrative.

      Where were you for all those Bennett Hassleton articles?

    • Wow, yeah science should never attempt to be interesting, especially for the lay audience. All of the longstanding questions, brilliant technological achievements, and research built on the shoulders of giants is completely worthless to talk about when all the had to tell us is "there's moving dust on it".

      In other news I wasted a whole 8 seconds reading that first sentence describing your unnecessary editorial opinion and post script. Your summary was twice as long as it needed to be.

      Seriously, 10 short lar

    • The moon has a side facing away from Saturn which is darker then the side facing saturn. It seems to be due to collecting dust from a larger ring that is on the border of its orbit.

      You said that very succinctly. Unfortunately it is also very wrong.

      Read TFA again. The dark side (of Iapetus-- not the Force) is the side that is facing forward in its orbit.

      May the Farce be with you.

  • THAT'S NO MOON!!!
    • right it is a egg, of a space dinosaur.

      that is why it has a ridge.

      • It was a poor attempt at a Star Wars reference...
        • Why people bother with Star Wars references remains beyond me. Like - it was a movie in the 1970s or so, with an unending stream of sequels and prequels and reboots and regurgitations. Do people still watch these things? If I wanted an unending sequences of prequels and reboots, I'd watch a Bond movie.
          • It is the same as people who keep shouting 'oh my gawdd', while that is just a very old-fashioned book from about two thousand years ago. Some things just make it into classics.
      • Actually, it's the embryonic stage of a Titan. Hopefully Iapetus will survive it's birth and not shatter into a second ring system...
  • by Anonymous Coward on Thursday February 05, 2015 @07:49AM (#48987653)

    We aren't all using tablets or phones. Looks like crap on my laptop.

    As for the article, if you are going to casually use words like "sublimate" without definition, it means your target audience is sophisticated enough that you don't need to write using a breathless, made for reality TV, annoyingly *excited* tone.

  • The Ridge (Score:5, Interesting)

    by Viol8 ( 599362 ) on Thursday February 05, 2015 @07:51AM (#48987659) Homepage

    POssibly the moon is formed from 2 bodies colliding and before it could completely settle down into a round shape it froze with that ridge remaining?

    • POssibly the moon is formed from 2 bodies colliding and before it could completely settle down into a round shape it froze with that ridge remaining?

      Nah, it's clearly an equatorial mass driver that was covered over with rock to keep it safe from meteorites.

  • mindblowing (Score:5, Funny)

    by dingleberrie ( 545813 ) on Thursday February 05, 2015 @08:08AM (#48987697)

    Dude... Do you think that when Pink Floyd sang about the Dark side of the moon, they were really talking about Iapetus?

  • by Anonymous Coward

    and unreadable hipster websites

  • by Anonymous Coward

    was Kieth.

  • It amazes me that so many allegedly "educated" people have fallen so quickly and so hard for a fraudulent fabrication of such laughable proportions. The very idea that a gigantic ball of rock happens to orbit our planet, showing itself in neat, four-week cycles -- with the same side facing us all the time -- is ludicrous. Furthermore, it is an insult to common sense and a damnable affront to intellectual honesty and integrity. That people actually believe it is evidence that the liberals have wrested the la

  • My armchair theory for the ridge would be it wasn't always tidally locked, and plowed through a significant amount of debris material along that plane originally. Eventually becoming tidally locked, and the larger particulate had been mostly thinned out. And the tilt happening as the rotation failed, much like a top wobbles and falls over after losing momentum.

  • This is wrong "Moons in our Solar System" should be either "Moons in the Solar System" or "Moons in our star system". I hate reading Sci-Fi books that has multiple solar systems in our galaxy. Tim S.
    • Even the NASA does not agree with you "A solar system refers to a star and all the objects that travel in orbit around it. ..."
      https://solarsystem.nasa.gov/p... [nasa.gov]

      If one day humans reach other solar or if you prefer star systems, then they likely will keep using the terms solar and sun to refer to their local star. A solar panel will never be renamed to something like an Alpha Canis Minoris panel.

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