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Saturn's Rings May Be Very Old

Posted by CmdrTaco on Tue Sep 23, 2008 03:23 PM
from the even-older-than-bob dept.
Space Science
Kristina from Science News writes "Combining computer simulations with data about the way starlight shines through Saturn's rings suggests the individual grains are big and thus could have been around a good 4 billion years, not the mere 10 million to 100 million previously suspected. What may have thrown earlier observations off is the chance that the grains aren't evenly distributed, but clump here and spread out there."
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  • That's not too surprising (Score:4, Funny)

    by moderatorrater (1095745) on Tuesday September 23 2008, @03:25PM (#25126665)
    Saturn was more faithful than Zeus in the mythology, it makes sense that it would have had its ring for a while.
  • The article seems to contradict itself:

    The origin and age of Saturns rings has been a riddle for decades, notes Jeff Cuzzi of NASA Ames Research Center in Mountain View, Calif. He notes that the gravitational interactions between particles in Saturns A ring and adjacent moons would transfer momentum from the rings to the moons, pushing the moons outward and slowing down the ring particles. If the rings were really as old as Esposito suggests, then the moons would be much farther away than they are and the A

    • You don't seem to understand journalism (Score:5, Insightful)

      by Moraelin (679338) on Tuesday September 23 2008, @03:55PM (#25127207) Journal

      1. It's not as much self-contradicting, as two different people are supporters of two different theories. One of them is obviously wrong, and they'll have to compare the evidence and find out who. In the end that's how science works.

      But at any rate, it's not that theory X contradicts itself. It's just that theory X contradicts established theory Y. Or at least someone thinks he has data which contradicts theory Y, and his own theory X explains better. That's expected. If it didn't contradict anything, it wouldn't be much of a piece of news, and probably the old one would fit Occam's Razor better.

      2. Well, you don't seem to understand journalism. These guys can't just tell you "X says Y", because that would violate their fucked-up notion of journalistic impartiality. They _have_ to present the opposite point of view too, even if they have to scrape the bottom of the proverbial barrel to have an opposing point of view.

      Because for these guys everything is an opinion. If they feature John Jackson saying "I say your 3 percent Titanium tax goes too far!", they have to bring in Jack Johnson saying "I say your 3 percent Titanium tax doesn't go far enough!" Well, in politics those _are_ opinions, but these guys have to do the same to science articles too. If they star someone saying, "the temperature is rising", they also have to find someone who'll go "no, it's sinking!" Or viceversa. If they feature someone who says, "power lines can't cause _allergies_, silly, because that's not how your immune system works. A protein has to bind to another mollecule, see.", they also have to drag in some crackpot who'll testify how he and his dog sneeze near power lines, and he's even in a crackpot group where they all can testify that they sneeze near power lines.

      Even if one or both are with degrees in gardening, bought from some fly-by-night diploma mill in Elbonia. And they can't tell you that, because that would already tell you who to believe, and that's against journalistic impartiality.

      In this case it's not that bad, and it's even relevant for a change. Because I'd assume the fellow from NASA _is_ in a position to know what he's talking about. But the basic principle is the same: if X says the rings are old, they can't publish that without finding someone else who says they're new. It's just how it works. In this case they actually found a scientist for the opposing point of view. But knowing modern journalism, that's more of a happy coincidence than the rule.

      3. While this may create (and does create) a lot of impression that there's a lot of controversy in science, and nobody knows anything for sure, that's really nothing lethal to science. That's how it's supposed to work. We don't know _everything_ already, or we could fire all scientists and be done with it. A theory at a given moment is just the one which best explains the existing data. When new data is found that it doesn't fully explain, we get to refine it into something better.

      That's really how we moved from, say, indivisible atoms, to the raisin-pie model, to the planetary model, to the modern quantum model. Each model was good enough for a given data set, but finding more data brought it into question. Until those Rutherford, Geiger and Marsden went and shot alpha particles through a gold foil, nobody ever suspected that the positive charge is concentrated in a small nucleus. Now we know better.

      The same happens here. For the data we had, the existing theory (which obviously Jeff Cuzzi represents) of new rings was good enough. Now someone found data which he thinks contradicts the existing one. It remains to be seen if he's actually right. Yes, there still is the possibility, of an "or not." But either way it's no loss. At the end of it, we'll learn a little bit more about the universe. That's the whole purpose of the exercise.

    • Or another way to look at it: the article is being honest and presenting evidence to the contrary. There are ways around Jeff's concerns, though.

  • Uranus! (Score:3, Funny)

    by orkim (238312) on Tuesday September 23 2008, @03:29PM (#25126757)

    Uranus jokes in: 3, 2, 1...

  • Why would they think they would necessarily be smooth. With the moons circling, comets flying by, Jupiter swinging around every so often. I'm surprised they're as evenly distributed as they are.

    • Re:Evenly distributed? (Score:5, Insightful)

      by CheshireCatCO (185193) on Tuesday September 23 2008, @03:50PM (#25127143) Homepage

      Over scales of tens or hundreds of meters, none of that mattes. The nearest known moons are in the outer edge of the A ring (Pan and Daphnis) and don't affect the B ring much (moons are too small). Jupiter has no effect at all being at least 4 AU away, generally more. The larger moons can muck things up, but the effects tend to be at resonances and are pretty localized.

      What Larry Esposito and others are talking about is localized clumping, more like what's known in the A ring. Over a scale of a few hundred meters, you wouldn't necessarily expect suck clumping to occur.

        • Agreed, which only re-enforces my idea below about why things migrate to disc shapes.

        • "No effect" is a reasonable way of avoiding clutter when the effect is many orders of magnitude less important than the dominant players. I figured the people who knew the difference would be able to connect the dots.

      • Gravity has little to do with the disk shape. Collisions drive the flatness. Collisions tend to average out speeds, so that eventually everyone moves in the same direction at almost the same speed. (In Saturn's rights, where speeds are tens of kilometers per second, relative collision speeds are at about a millimeter per second.)

          • Re:Evenly distributed? (Score:4, Informative)

            by CheshireCatCO (185193) on Wednesday September 24 2008, @09:45AM (#25135991) Homepage

            This will cause them to adjust their orbits to match. Well duh, right?

            Actually, no. That isn't what happens, in spite of your intuition. The moon's response to the rings is largely to have a more rapid vertical motion than it would around just the planet. (This can be worked out for an embedded moon/planet in a disk using a Gaussian pillbox argument. It's a classic galactic dynamics question for undergrads, in fact.) There are more effects possible, depending on the relative masses and locations. For example, the moon can launch bending waves in the ring of material, which can then tug back on the moon. This can either pump up or damp down the moon's inclination. (Which isn't obvious and depends on a variety of parameters in the system.) The moon can also cause warps in the ring, but those tend to wind up pretty fast.

            On the other hand, people *have* simulated rings. (Including myself, I might add.) You find that gravitational encounters between particles in the rings actually pump *up* the ring thickness. It's only with dissipative collisions that you get the ring to collapse down.

            Your objections to the Cosmic Microwave Background are probably fodder for a different discussion, but it's difficult to see how that data shows evidence of a galactic collision, given the low energy involved (and the precise match to the predictions of the Big Bang). You should probably be worried that you're letting your desires for how the universe *should* be make you closed to what the data say it probably *is*. It's a very human response, but one that works contrary to good science.

  • then who knows whats floating around in those rings, there might be some good clues to the nature of this star systems construction in there...

    • Re: (Score:3, Informative)

      by CheshireCatCO (185193)

      Not likely, the ring particles have been bouncing off of each other for a long time. Saturn's rings are dynamically-speaking one of the oldest systems known (meaning each particle has made lots of orbits) and collisions occur on the scale of at *least* a few per orbit per particle in the B ring. (If clumping is occurring, it's even higher.) So the particles will probably have evolved from that alone. Plus, we don't know where the ring material came from. There's reason to think it was from an earlier

  • What may have thrown earlier observations off is the chance that the grains aren't evenly distributed, but clump here and spread out there.

    I wish they would both clump and spread there, and not here.

  • They're very old, astronomers just didn't realize it because they were stored in mothballs [slashdot.org]
  • ... The Sun may be very very hot.
  • get off my rings!

  • I don't know much about the Cassini mission but I would imagine that they wouldn't want to jeopardize the probe by sending it too close to the rings where debris might damage her. You know what'd be cool though? If they could send in a reinforced probe similar to the Giotto probe that flew into Halley's Comet, send it as close to the rings as they can with a good telescope on board. I'd love to see actual close-up photos of the rings and see how accurate a prediction that artist's impression is.

  • Clearly they mean 6000 years?

    • No, they weren't. Previous theories were based on the spectra of the particles (stuff left in space gets 'weathered' with time due to meteoritic dust and high-energy particle/photon alterations) and to dynamical arguments. What this study has suggested is that the spectra are misleading because the material that's exposed now may not have always been on the surfaces.

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