Just how old are Saturn's rings?

By Phil Plait | September 23, 2008 1:00 pm

Something that has bugged me lately is the idea that Saturn’s rings are young, like maybe 100 million years old. I talked about this in a recent video I made about Saturn, in fact.

You can’t just count them to get the age, y’know.

It bugs me because Saturn’s rings are gaudy and obvious, spectacular and awesome. It seems really unlikely that they are so young, compared to the fantastic age of the solar system (4.55 billion years). It’s too much of a coincidence to think that they happened to exist just when we happen to be around to see them.

Astronomers don’t like coincidences. It’s usually more likely that we’re missing something.

In this case, that might very well be right: we are missing something. Or, more accurately, our models of the rings are missing something: like, 2/3 of the mass of the rings.

A new study from the University of Colorado indicates that the way we’ve been thinking about the rings may be slightly in error. Usually, people think of them as countless individual chunks of ice. However, in the new CU study the chunks tended to cluster together, forming aggregate clumps of particles.

Ring particles may like to stick together.

Oddly, this makes a huge difference in our results. For one thing, if this is correct it means the mass of the rings has been underestimated. The rings may be two to three times as massive as previously thought. The mass has been determined by measuring the amount of light absorbed by the rings when a star passes behind them. More absorption means more material. But this also depends on the distribution of the particles; if they clump together, they can be far more massive in total and still absorb light the same amount as individual particles do.

So the rings may be 3x as massive as we used to think. But that also affects how old we think the rings are! The age of the rings is estimated by how reflective they are; the idea is that meteorite impacts grind up the ice particles, and also leave meteoric dust covering the particles. Over time, the dust drops the reflectivity of the particles. By measuring how reflective the rings are, you can estimate the age. The rings are shiny and bright, so it’s been assumed they are young. But the new models show that the more massive ring clumps can be old and still look shiny, despite being pelted by meteorites.

This study is pretty new, and may or may not pan out (astronomers are still comparing this model to observations of the rings to see if everything hangs together). But like the previous post I wrote about Mercury’s spider, this new model does explain some things about Saturn’s rings that are currently uncomfortable. I use that word on purpose: it’s entirely possible that the rings are young (if 100,000 millennia can be considered young). But that seems unlikely, and that discomfort can spur on more research that yields better insights and results closer to truth. I don’t necessarily trust those kinds of instincts or feelings, but it does pay to investigate them!

CATEGORIZED UNDER: Astronomy, Science

Comments (58)

  1. tacitus

    See, now, this is yet another example as to why the certainty of the creation model for the solar system is sooo much better than all this waffling, hedging, and prevarication coming from those evil liberal scientists. And it just proves that they will do and say anything rather than accept yet more evidence that things in the solar system are *younger* than they expected…

    [/sarc]

  2. Ticknick

    Other giants have rings too. According to whatever source, those rings would have formed quite recently too?

    I can recall an item about a study that claims the rings of Saturn are renewing all the time. I don’t know where the debris (it must be quite some) comes from then. I guess the moons are vacuum cleaners.

  3. Would a similar finding throw off mass estimates for dust throughout the universe?

  4. Gnat

    This is so cool! Aggregates and reflectance are principles in my field too…paint! Aggregates in a paint grind can impact the TiO2 reflectance. In a nut shell, I love how principles for the solar system are the same on a much smaller scale. (And I get to feel like a mini-astronomer!) :)

  5. Robert Krendik

    These are my favorite topica you write about, the planets!

  6. The thinking on Saturn’s (and other planets’) rings has evolved over the years. Esposito (the guy whose work you’re taking about) was one of my profs at CU, and I remember his lectures about the dynamical evolution of the systems. At one time the thinking was as you described — that they are young and much more ephemeral than suspected and because they’re so bright, they must be young. Competely understandable assumptions to make, given what we knew about them at the time. But, I think that stemmed from just not having enough data about them, and incomplete models.

    I don’t know that I’d characterize our thinking as “erroneous” (however slightly). More like “incomplete” and that’s not all bad. I mean, we are still filling in chinks of our knowledge about the solar system.

  7. I do love that photo of Saturn…

  8. IVAN3MAN

    The above picture of Saturn was featured as the Astronomy Picture of the Day on October 16, 2006. The link will lead you to it, and by clicking on that picture it will “embiggen” it further to reveal the “Pale Blue Dot” of Earth — just above and to the left of Saturn’s rings. Cool!

  9. Sean

    Has there been any talk of getting Cassini to fly really close to the rings to look at them within a very narrow distance or is that not possible?

  10. IVAN3MAN: more importantly it was my top pick for astrophoto of 2006. :)

  11. Michael W

    BA, One of the problems I had in high school resolving science and belief are captions like you put on the second image.
    The particles may be attracted to each other, but do they “like” it?
    The other one that always got me was the lighting “finds” the shortest path to ground, does it check google earth first?
    Using words that attribute intelligence to a natural phenomenon, help cloud the science and give IDers are starting point.

  12. Michael W: Yes! Down with the pathetic fallacy!

  13. Unless I’m missing a zero somewhere, 100 million years doesn’t seem very unlikely to me. The Earth’s age is (round numbers) 5 billion; 100 million is 2% of that. Keeping the human-civilisation point fixed, the probability that Saturn will have rings at any given point in the five-billion-year history is then 2%, or even 4% when you consider the full lifetime of the rings. (That is, I assume they will be around for as long as they have already survived.) You expect to see quite a few four-percent chances coming up over something the size of the Solar System, surely? The odds aren’t exactly – ha-ha – astronomical.

  14. Gary Ansorge

    Michael:
    Like is a euphemism for attraction.
    Shortest path to ground is somewhat of a misnomer, as lightening(I presume that’s what you meant) can travel 20 miles from cloud to ground, while the cloud itself is only a few miles above earth. It has to do with the dielectric of air, not the absolute distance to earth.

    Personification of inanimate objects is a natural human attribute. Many name their cars, (though my 1980 Blazer is just called “Tank”). I doubt most people really think their cars are “intelligent”.

    GAry 7

  15. Mark B

    This is weird, I had always thought that we were living in a time frame where we were lucky to see the rings ( due to their youth and short lived period ) I must have picked that up from somewhere and not just recently I’m talking years ago.
    I’m gonna have a dig around but I am quite shocked to say that Saturns rings are not accepted as young.
    This is why I love sites like this and also the sister site at BAUT. You always have to challenge what you think is fact.
    More power to you Phil you do a sterling job here, I have two sons aged 7 and 10 and they both enjoy reading this site with me :-)

  16. Gary Ansorge

    Addendum:

    I wonder why anyone would be at all surprised that the ring components would be attracted together. Isn’t that how the solar debris cloud formed planets?

    GAry 7

  17. Wanglese

    Simple.

    Arthur C. Clarke described it. The rings were made by the same “people” who put the Monolith on Iaeptus, when they first visited and taught Moonwatcher how to hunt.

    You know, the monolith we should be looking for?

    Why else would they have made the rings, other than as a great big “LOOK HERE!” sign?

  18. Michael W

    GAry 7,
    First of sorry for the bad spelling (spell checker doesn’t help when it’s the wrong word).
    My comment was aimed at children trying to learn about science, and how the wrong words can confuse the issue.
    Many times I asked by high school physics teacher how does lightening “find” the shortest path to ground, without adequate explanation. I was trying to figure out what “sense” it uses to “find” ground.
    Only later did I realise that it was the emotive/intelligence words that was confusing me (as well as my teacher).
    If I had not struggled to find the answer, I would have continued to assume that there was some intelligence guiding the lightening. This then all folds back into the ID crowds lap, as they will point to the “designer” as the source of the intelligence.

  19. IVAN3MAN

    @ Michael W

    I had the same problem with Dr. Plait’s previous post about Mercury’s spider webs.

  20. IVAN3MAN

    Gary Ansorge:

    Personification of inanimate objects is a natural human attribute. Many name their cars, (though my 1980 Blazer is just called “Tank”). I doubt most people really think their cars are “intelligent”.

    You mean like Basil Fawlty and his car? –

  21. MarkH

    I seem to recall, watching NASA channel I think, on of the astronauts fooling aroung with different substances. One of these substances was ordinary table salt. One of the scientists was commenting on how the salt particles tended to clump together.

    I wish I could remember for sure where I saw and heard this. Maybe The BA or other scientist types could elaborate on this.

  22. C

    Wait a minute…

    What’s wrong with saying the rings are recent? Why couldn’t they be recent? Just because “Astronomers don’t like coincidences”? Just because it’s unlikely doesn’t mean it didn’t happen recently. The evidence is there: other planets with rings in various brightnesses, almost as though the zoo of moons around each is constantly producing collisions and rings that eventually spiral into the planet; the brightness of Saturn’s rings, pointing to a relatively recent event, and so on. Lots of stuff has happened recently for us to see it, even in this tiny neck of the woods. Jupiter got smacked by a large projectile in the last century. So did Siberia.

    I’m uncomfortable with scientists looking for something in the rings that may not be there, just to make themselves feel comfortable.

    Reminds me of creationists.

  23. SF Reader

    Sean:
    @Has there been any talk of getting Cassini to fly really close to the rings to look at them within a very narrow distance or is that not possible?

    At one point, they navigated Cassini through the Cassini gap! That’s about as close as they want to get…

    Dennis

  24. tacitus

    There has been some talk of it, but it would be just about the last thing Cassini does at the end of the mission, since it would likely mean the end of the spacecraft. But no doubt maneuvering into a posting to take a close-up of the rings would cost a fair amount of fuel, and I suspect there are higher, safer priorities to deal with.

    It would be really cool if they could do it (i.e. sail close enough to the rings slow enough to image individual particles), but I suspect it’s not feasible. In any case, I’m willing to bet they can infer an awful lot from the images of the shepherd moons and how they are interacting with the rings they accompany.

  25. StevoR

    Phil Plait Said on September 23rd, 2008 at 3:52 pm :

    IVAN3MAN: more importantly it [That awesome image of Saturn with its rings backlit & Earth’s pale blue dot hiding in one of the gaps was my top pick for astrophoto of 2006.”

    Mine too! I just love that photo in fact I’d describe it as at least the image of the decade if not the century! ;-)
    (Yeah I know we’ve still got another 92 years to go til the end!)

    I am very surprised that it hasn’t even been featured as a poster in any of the’Astronomy magazines I regularly buy. (These are Astronomy, Astronomy Now, Sky & Space, Australian Sky & Telescope, Patrick Moore’s BBC Sky At Night & the odd other mags too!) Well at least not unless I’ve missedan aissue somewhere which idon’t think idid or missedseeingit it on one – ditto.

    Personally I would really love to get that spectacular shot in poster or even mural form – does anyone here know if that can be done?

  26. StevoR

    Interesting post here too Phil, as I’ve said before, I’d love to see you turn the best of these blog posts into another book …or even series of books! Just imagine – ‘Best of the BA blog’ volumes I to 100! ;-)

    As far as co-incidence goes – wouldn’t the oddest and least likely thing be if there were *NO* co-incidences!?

    One of the best astronomical co-incidences as far as I’m aware is that the Sunand Moon have almost exactly the same apparent size inthesky and are thus abvle to eclipse each other.

    As for the age of ring systems in our solar system there was a page or two (pages 52-53) on this in Nigel Henbests non-fiction book ‘The Universe : A Voyage through Time & Space’ (Weidenfeld & Nicolson ltd, 1992) discussing this topic and simulating the evolution of the ring system of Neptune showing it with no rings, a Saturn-like fresh ring system circa 1,000 million years ago and then an older and now darkened ring system 500 million years on from the ring-creating event .. which, btw. it still has.

    All the gas giant and some ice dwarf planets – (in order of brightness where known I think) Saturn, Jupiter, Ouranos, Neptune & Pluto – have rings as does one of Saturn’s moons. (Rhea?) Can we date the age of their ring systems by how comparatively bright they are? Have we done this?

    Are there any plans to get samples of the rings from each to check and confirm such dates – that’d make a really awesome future mission or set of missions for NASA or other space agencies to conduct!

    PS. Have the theorised or detected rings of Pluto and that Saturnian moon been confirmed and have they been observed / imaged since?

  27. C said, “I’m uncomfortable with scientists looking for something in the rings that may not be there, just to make themselves feel comfortable.

    Reminds me of creationists.”

    Come on, it isn’t that bad. Even Einstein brought up the god, dice and universe thing. Not being comfortable and emphatic denial are two completely different things. Remember most discoveries don’t start with a “Eureka” they start with a “that’s funny….”

  28. a lurker

    While the new explanation might be cool, had the rings really been only 100 million years old it would not have bothered me one bit. As someone pointed out out that is about 2% of the history of the solar system. That comes out to a one in fifty coincidence. But wait, there are four gas giants. So lets divide by four. That is one in 12.5.* Hey, is there any reason why this could not happened more than once? Maybe 3 billion years ago there was a similar ring system that lasted a 100 million years? So I really can’t see the rings as being more than a one-in-ten coincidence at worst.

    But lets say that the rings really hugely impossible. There are countless things in the Solar System. There is no way that something widely spectacular but improbably could not have happened. We humans would have latched on to something as “too improbable.”

    How many things could possibly existed in the Solar System that would make Phil Plait go “wow” but don’t actually exist. I am sure the number is very high. So we really should take into account all the probabilities for things which an alternative universe Bad Astronomer would write a post like this one about.

    * Or to be more mathematically correct, 1-(1-.02)^4=1/12.9.

  29. linusrp

    Well, it is not the possibility of the rings being young that bothers the scientists, nor is it the possibility that we can observe them. It is more that it is unlikely that those two thing happens at the same time that bothers. But even that is not a problem, it is just something that stirs the curiosity in scientists, because there might be a more “correct” explanation. Off course if it turns out that the rings are young then that is not a problem, just interesting and odd.

  30. Wanglese Says: “Arthur C. Clarke described it. The rings were made by the same “people” who put the Monolith on Iapetus, when they first visited and taught Moonwatcher how to hunt. Why else would they have made the rings, other than as a great big “LOOK HERE!” sign?”

    IIRC, the rings were created as a byproduct of setting up the monolith on Iapetus. In chapter 37 Clarke writes: “For three million years, it had circled Saturn, waiting for a moment of destiny that might never come. In it’s making, a moon had been shattered, and the debris of its creation orbited still.” He goes on to say how they “burned” one half of Iapetus (Clarke calls it “Japetus” using the German spelling he learned from Wily Ley) so that it would flash black-white-black-white as a beacon to draw attention to the monolith’s location.

    - Jack

  31. FrankZA

    I thought the first picture of Saturn was fake. Damn… Awesome…

  32. owlbear1

    Wouldn’t a 3x more massive ring system mess with Cassini’s orbit?

  33. Rob

    C – it’s to do with probability.

    If the rings only last 100,000 years then the odds of them being visible at the time we are looking are 100,000/4.5 billion, or 1 in 45,000. That’s a very low probability, which makes astronomers uncomfortable, as the BA puts it.

    But all four giants have rings, so the odds of seeing them all with rings at the same time (assuming the probabilities to be independent) are 1 in 4.1 x 10^18 (4.1 billion billion). That’s getting pretty ‘uncomfortable’.

    There are two or three ways out of this. One: some event triggered the formation of rings on all four planets in the recent past. Two: the rings are older than they look (as in the BA’s current post). Three: the rings are continuously renewed by some process. All of these means something is ‘missing’ that we want to go looking for.

  34. John Phillips, FCD

    @C: The difference is that when scientists feel uncomfortable with something it just means that they are going to look even harder to see if there is a better explanation. If there is, great, if there isn’t, then so be it. Most scientific discoveries have been because of someone feeling uncomfortable with an existing or no explanation and looking for one. On the other hand, when the average creationist feel uncomfortable with something they just say goddidit, theirs not to reason why.

  35. Gary Ansorge

    C:
    I’m uncomfortable with scientists looking for something in the rings that may not be there, just to make themselves feel comfortable.
    Reminds me of creationists.

    Elegance is an aspect of reality that correlates with the structure of the observing nervous system. ie, the theory of relativity is “elegant” because it explains so many observations so precisely and simply. On the other hand, the necessary inclusion of a cosmological constant was “inelegant” because it had to be inserted w/o implicitly arising from the mathematics of relativity. Sort of like having to add a minor chord to a piece of music in order to force an acceptable resolution of the progression. It just doesn’t feel right and implies we’re missing something that could make better sense if we only looked a bit harder/smarter.

    If there is a god, that (lack of ) elegance might be one way that such a one could try to impel its creatures to look a little deeper. On the other hand, the development of complex nervous systems must likely be in accord with the essential structure of reality in order to resonate with that reality in a “truthful ” way,,,ever notice how politicians just seem to irritate when they’re speaking? Like fingernails on a blackboard, their lies are inelegant and ugly,,,and contrary to reality,,,

    GAry 7

  36. Gary Ansorge

    Ivan3Man:

    Yes but notice, the branch does no damage to the car,,,it’s obvious he understands there is really no “fault” on the vehicles part. It’s dead, dumb and non-sentient, so beating it will do no good but don’t damage it. Tomorrow he will have to pay to repair it.

    Still, we’re likely ALL guilty of taking joy in beating a rock. Mainly because it can’t beat US,,,

    Gary 7

  37. Sarcastro

    I’m uncomfortable with scientists looking for something in the rings that may not be there, just to make themselves feel comfortable.

    Reminds me of creationists.

    It does have the mark of an argument from incredulity. I don’t, however, consider such an argument to be an invalid metaphysical hypothesis. It is perfectly OK to begin one’s research by noting that current research doesn’t make sense to you and to go on and do physical experiments to see if there might be a different cause. Metaphysics is, after all, the queen of science. What’s not copacetic is to end one’s research with such an observation by leaping immediately to “so it must be God”.

  38. madge

    Do you suffer from unsightly clumpy rings? Try NEW Ringo Clumpaway! Just one squirt and BANG the clumps are gone! Enjoy smooth clumpfree rings the easy way. BUY NOW! :D

  39. C: I think you’re confusing “discomfort” with “don’t believe” when it comes to coincidences. I think that Garek on Deep Space Nine (me = nerd) said it best: “I believe in coincidences. Coincidences happen every day. I just don’t *trust* coincidences.” That’s pretty much where scientists are: coincidences make us nervous and make us ask questions, but a good scientist doesn’t reject an interpretation of the data just because it involves a coincidence.

    Also,

    Gary Ansorge:
    I wonder why anyone would be at all surprised that the ring components would be attracted together. Isn’t that how the solar debris cloud formed planets?

    Yes and no. The problem there is that unlike the planets, rings are highly affected by the planet’s tidal forces which work to pull apart and clumps that form. In fact, in N-body simulations, you can watch clumps form in the A ring and then tear apart as they get stretched out all on the timescale of a single orbit. (It’s a bit more complicated than that: the stretching occurs in the orbital direction, not radially, and is due to the differing orbital velocities.) The effect should be even more pronounced in the B ring, being closer to Saturn, so you’d expect less clumping to occur.

  40. SteveG

    I have to agree in principle with C.

    Ok, I’m all for skepticism and I too don’t like coincidences.

    But two points about your discomfort leap to mind, BA.

    Point one: Being skeptical of something only because it seems to have arrived just in time for us to see it seems to me like the other side of that familiar coin that would make others feel they were placed there just SO we could see them. (Never mind that rings around planets, at least in our solar system are not uncommon so it may not be such a coincidence after all.) I’m sure you have other reasons for wanting to test the theory regarding the age of the rings and it sounds like a good idea given that the age estimates are based on several assumptions. But Just because something happens while we’re around doesn’t automatically make it suspicious anyd more or any less than it makes it designed for us. Were you uncomfortable when Shoemaker Levy hit Jupiter just when we could observe it? Don’t get me wrong, I’m a strong skeptic and we all know you are too. But the way you worded your suspicion just bugged me.

    Point two: The whole idea of basing any belief or any suspicion on whether or not humans are around seems to me to be rather anthropocentric thinking. Whether or not humans are around to observe something has nothing to do with anything. I don’t see how it even enters into the conversation.

    Just my two cents…

  41. Remember what they (who the hell is they?) say,
    Once is an accident
    Twice is a coincidence
    Three times is a conspiracy.

  42. Surely, the rings of the giant planets evolve rapidly when compared to the whole solar system. Moonlets are continously captured and smashed to form rings . Currently, we begin to have a deeper vision of solar system evolution: the relationship between comets and centaurs, the origins of the Kuiper belt objects (KBOs), the fate of moons such as Phobos (Mars) or Trito (Neptune), etc. And, after all, for me it is very difficult to imagine a Jupiter without the Red Dot or the Earth with a single continent (Pangea).

  43. Todd W.

    Well, see. Saturn isn’t actually a planet. I’m sorry, but it just isn’t. See, the rings are evidence that it is still in the process of clearing its neighborhood. The fact that they’re still around means, of course, that there is still stuff around for it to pick up. :P

  44. Tim G

    Do you suppose that Saturn’s rings could be a recurrent phenomenon? If so, a relatively young ring system would not be that big of a deal. There could also be phenomenon which we don’t see presently. I wonder how likely Jupiter will acquire a very bright ring system. Unfortunately, Jupiter’s 3° tilt means that it would not appear too much brighter as seen from Earth.

  45. Point two: The whole idea of basing any belief or any suspicion on whether or not humans are around seems to me to be rather anthropocentric thinking. Whether or not humans are around to observe something has nothing to do with anything. I don’t see how it even enters into the conversation.

    I think you’re the one putting the undo importance on humans, here. The argument about coincidence is all about probability: if you tell me that over the entire age of the solar system, a particular feature would only have been there for 1% of the time, I’d be surprised if I actually saw it the one time I got to look. This may make me question your statement some. (Maybe the feature has been there longer or appears and disappears?) Now, it doesn’t tell me you’re wrong, but it does make me want to dig deeper. And that’s the point.

    Put it another way: if I play a betting game with you with what I say is a fair coin and yet the coin comes up heads (letting me win) 20 times in a row, wouldn’t you wonder if maybe I lied/was wrong about the coin?

    (Also, an aside, but Shoemaker-Levy 9 is a bad analogy. Astronomers saw it, to be sure, but we also believe that such collisions happen a lot. So not really a much of a coincidence.)

  46. bjn

    1/45,000 odds contains assumptions that seem rather silly. We have rings around other gas giants, why assume that bright rings formed only once any gas giant in four and a half billion years?

    As to long odds, what’s the problem? Our being around with technology to view a a comet break up and strike Jupiter was incredibly long odds depending on all the contingencies you wish to calculate. For that matter, you can get all anthropcentric and work out the odds so the clockwork of the universe is so improbable that it has to be designed for little ol’ humanity. Heck, you can take the same tack and argue that you yourself have to be at the center of the universe – what are the odds that you’d be alive at this time, yadda, yadda, yadda.

    I say it’s big universe and a big solar system and it would be absurd not to expect some fortuitous (for us) coincidences. This reminds me of the unproductive stand that geologists have traditionally taken against catastrophic events on this planet in favor of extremely slow geologic processes. The source of geologists’ discomfort was contention with biblical folks who invoke “the Flood” as the cause for geologic formations. Astronomers have had to similarly deal with strong anthropocentrism from the same religious context. But I think the case is well made that universe is too old and too vast for humanity to be anything but an interesting byproduct of unfolding universal processes. I don’t think anyone should feel uncomfortable with an interesting coincidence here and there. You know, like the moon being at the right distance and size to nicely block the sun. It’s cool and the odds have to be extremely long against my being alive to see an eclipse, but that just makes me appreciate it more.

  47. Todd W.

    @bjn

    “I say it’s big universe and a big solar system”

    Reminds me of Animaniacs: “It’s a great, big universe, and we’re all really puny. We’re just tiny little specks about the size of Micket Rooney…”

    Ahh…great show.

  48. Todd W.

    Sorry…should’ve been Mickey Rooney, not Micket….

  49. Thomas Siefert

    Do you suffer from unsightly clumpy rings? Try NEW Ringo Clumpaway! Just one squirt and BANG the clumps are gone! Enjoy smooth clumpfree rings the easy way. BUY NOW!

    Disclaimer: (the fastest voice on earth) notforuseonnonringedplantesandnotforinternalconsumptionbutcanbeusedonuranus

  50. dkary

    As someone who used to work on ring dynamics back in the pre-Cassini era, I have to agree with the assessment that folks in the field simply were certainly prepared to accept the 100 million year age for Saturn’s rings, and indeed plenty of work was done on ways that such a ring system could form. However, it was also clear that there were a lot more opportunities for such a big ring system to form much earlier in the solar system’s history: there was simply a lot more junk available that could be ripped up by Saturn’s tides.

    So the “discomfort” that a lot of us in the field felt about this wasn’t just because it was a 1 or 2% probability of being around in the right time frame. It’s that the sort of event that could produce these rings is much more likely in the first few hundred million years of the solar system’s history than it is now.

    Now if newer data had simply confirmed that the rings are young, sobeit. As others have pointed out, a certain number of individually unlikely things have certainly happend in our solar system (the formation of our Moon is a good example here), so with a whole solar system to choose from we’re bound to find a few. However, there is always going to be a suspicion whenever you’ve got such an unlikely event that you might be missing something important here.

    I don’t know how much this will translate into the other giant planet ring systems: they really are very different kinds of beasts (from each other as well as from Saturn’s main rings). Something like the dust-dominated gossimer ring of Jupiter has a lot of very different physical processes acting on it than the ones that have been applied here.

    DK

  51. Don Snow

    The rings around my shirt collar don’t clump. Is something wrong with the ring around my shirt collar?

    OK, I’m going to get brave.

    I’ve had an idea for about 12 years. Haven’t discussed it. It came up, when I learned that some gas giants in M52 do not orbit stars in the nebula.

    Statement: there are not enough debris in the asteroid belt, for the asteroids to have resulted from a planet.

    Speculation: gas giant floats out of M52, through interstellar space and through our solar system. On the way through, it’s near by passage to Aster breaks up the planet; most of the pieces follow the rouge gas giant. As it passes Jupiter and Saturn and Neptune, these gas giants pull some of the debris from Aster to themselves, from the rouge. The rouge floats on out of the solar system, taking the rest of the debris from Aster with it.

    This scenario may be placed at any frame of time. If 100M year ago, it would explain the youth of the rings on all our gas giants.

  52. amphiox

    1. Don Snow: Your idea is intriguing but as a scientific hypothesis it runs afoul of the principle of parsimony. First, there is no a priori reason for there to have to have been extra mass in the asteroid belt, so no need for a special mechanism to explain it. Even if there were, Jupiter alone would have been sufficient to do the sweeping. (At any rate, of all the asteroids were combined together into one body, that body, though substantially smaller than earth’s moon, would nevertheless have been easily a planet by anyone’s criteria. One can even think of Ceres as the protoplanet that would have grown into this planet, except that Jupiter’s gravitatational influence on the region prevented it from happening.)

    2. The coincidence of all the giant planets having rings isn’t quite as stringent, because current theory considers them each to be of different age. Saturn’s, at 100M years, is the youngest. The other ring systems are substantially older, making it that much more probably for all four giant planets to have ring at present.

    3. Even if ring systems are ephemeral and Saturn’s very young, it doesn’t constitute that great a coincidence that we observe them. Since there is nothing particularly special about the mechanisms believed to be responsible for forming rings, there is nothing to prevent ring systems from forming repeatedly. Even if individual rings only last for a short period of time, in the lifetime of the solar system, a planet like Saturn may have had rings hundreds of different times.

    4. If Saturn’s rings generate unease because of their seemingly remarkable coincidence, then does the current temporal-spatial coincidence that makes the moon and sun appear to be the same size in the sky, generating that eclipse image some religious wackos try to equate to the eye of god, cause similar unease, and are there astronomers out there developing theories to more elegantly explain that observation?

  53. One thing that seems curious to me is how the age of the rings is estimated. It seems to be based on albedo. The older they are the darker they become because they get coated with darker silicate material from meteoroids. At least that’s my understanding of the process. So a young age is deduced via a high albedo (i.e., very reflective). This would seem to depend on some factors we probably don’t know to high precision:

    1.) The albedo of the meteoroids in the vicinity of Saturn (if this value is high then even highly reflective rings can be very old)

    2.) The density of meteoroids in the vicinity of Saturn (this affects how many impacts with ring objects occur over some period of time)

    So without direct sampling of nuclear decay in the ring particles estimating their ages seems a bit chancy with the poor data we have at the moment.

  54. One other phenomenon which has not been mentioned is Phobos:

    http://en.wikipedia.org/wiki/Phobos_(moon)#Future_destruction

    “Phobos’ low orbit means that it will eventually be destroyed: tidal forces are lowering its orbit, currently at the rate of about 20 meters per century, and in 11 million years it will either impact the surface of Mars or (more likely) break up into a planetary ring.”

    11 million years out of 4.5 billion is 408 to 1 odds against. The odds that we exist at a time when we can see Phobos are 408 to 1 against. I haven’t heard that this fact is making astronomers “uncomfortable”.

  55. I haven’t heard that this fact is making astronomers “uncomfortable”.

    I have, as a matter of fact. A fellow astronomer (non-dynamicist) once asked me about that exact issue.

    1.) The albedo of the meteoroids in the vicinity of Saturn (if this value is high then even highly reflective rings can be very old)

    Eh, what the meteroitic dust does to the color isn’t that poorly known. The range of possible albedoes is so small compared to the difference between pure ice and dust that it shouldn’t matter much.

    2.) The density of meteoroids in the vicinity of Saturn (this affects how many impacts with ring objects occur over some period of time)

    This is a bigger unknown (although you can estimate the rate from surfaces whose ages are based on crater-counts). Still, you’re probably talking a factor of 10 in uncertainty, which still doesn’t include the age of the solar system.

    Also, remember that that’s one out of two lines of evidence for the young ring model. The other, dynamics of spreading, is based on totally different physics.

  56. “Eh, what the meteroitic dust does to the color isn’t that poorly known. The range of possible albedoes is so small compared to the difference between pure ice and dust that it shouldn’t matter much.”

    Not if the meteoritic dust is composed of ice itself. Why do you assume that meteoritic dust in the vicinity of Saturn is the same as meteoritic dust in the vicinity of the Earth?

    “Also, remember that that’s one out of two lines of evidence for the young ring model.”

    I seem to recall an article on the NASA Cassini site where they found evidence that the rings are 4.5 billion years old. That seems to contradict a lot of the young ring claims.

    http://www.nasa.gov/mission_pages/cassini/media/cassini20071212.html

    Saturn’s Rings May be Old Timers
    12.12.07
    SAN FRANCISCO, Calif. – New observations by NASA’s Cassini spacecraft indicate the rings of Saturn, once thought to have formed during the age of the dinosaurs, instead may have been created roughly 4.5 billion years ago, when the solar system was still under construction.

    Larry Esposito, principal investigator for Cassini’s Ultraviolet Imaging Spectrograph at the University of Colorado, Boulder, said data from NASA’s Voyager spacecraft in the 1970s, and later from NASA’s Hubble Space Telescope, led scientists to believe Saturn’s rings were relatively youthful and likely created by a comet that shattered a large moon, perhaps 100 million years ago.

    But ring features seen by instruments on Cassini — which arrived at Saturn in 2004 — indicate the rings were not formed by a single cataclysmic event. The ages of the different rings appear to vary significantly, and the ring material is continually being recycled, Esposito said.

    “The evidence is consistent with the picture that Saturn has had rings all through its history,” said Esposito of the University of Colorado’s Laboratory for Atmospheric and Space Physics. “We see extensive, rapid recycling of ring material, in which moons are continually shattered into ring particles, which then gather together and re-form moons.”

    Esposito and colleague Miodrag Sremcevic, also with the University of Colorado, are presenting these findings today in a news briefing at the meeting of the American Geophysical Union in San Francisco.

    “We have discovered that the rings probably were not created just yesterday in cosmic time, and in this scenario, it is not just luck that we are seeing planetary rings now,” said Esposito. “They probably were always around but continually changing, and they will be around for many billions of years.”

    Scientists had previously believed rings as old as Saturn itself should be darker due to ongoing pollution by the “infall” of meteoric dust, leaving telltale spectral signatures, Esposito said. But the new Cassini observations indicate the churning mass of ice and rock within Saturn’s gigantic ring system is likely much larger than previously estimated. This helps explain why the rings overall appear relatively bright to ground-based telescopes and spacecraft.

    “The more mass there is in the rings, the more raw material there is for recycling, which essentially spreads this cosmic pollution around,” he said. “If this pollution is being shared by a much larger volume of ring material, it becomes diluted and helps explain why the rings appear brighter and more pristine than we expected.”

    Esposito, who discovered Saturn’s faint F ring in 1979 using data from NASA’s Pioneer 11 spacecraft, said a paper by him and his colleagues appearing in an upcoming issue of the journal Icarus supports the theory that Saturn’s ring material is being continually recycled. Observing the flickering of starlight passing through the rings in a process known as stellar occultation, the researchers discovered 13 objects in the F ring ranging in size from 27 meters to 10 kilometers (30 yards to six miles) across.

    Since most of the objects were translucent — indicating at least some starlight was passing through them — the researchers concluded they probably are temporary clumps of icy boulders that are continually collecting and disbanding due to the competing processes of shattering and coming together again. The team tagged the clumpy moonlets with cat names like “Mittens” and “Fluffy” because they appear to come and go unexpectedly over time and have multiple lives, said Esposito.

    Esposito stressed that Saturn’s rings of the future won’t be the same rings we see today, likening them to great cities around the world like San Francisco, Berlin or Beijing. “While the cities themselves will go on for centuries or millennia, the faces of people on the streets will always be changing due to continual birth and aging of new citizens.”

  57. Not if the meteoritic dust is composed of ice itself. Why do you assume that meteoritic dust in the vicinity of Saturn is the same as meteoritic dust in the vicinity of the Earth?

    This stuff has been observed, as I noted earlier. It’s definitely dark (even ice dust would be reddened pretty heavily from high-energy particle alteration), and it’s falling on the Saturnian system. We don’t know the rate precisely, that’s a far criticism. (Cassini tried to measure it during cruise, but that didn’t work out.) But to claim we don’t know that it’s dark or that we have no idea of what the infall rate is seems insulting to the researchers who have actually made strides toward just that.

    I seem to recall an article on the NASA Cassini site where they found evidence that the rings are 4.5 billion years old. That seems to contradict a lot of the young ring claims.

    You’re quoting the exact same researcher that Phil’s original post was about. That’s not really supporting your case any more than before. Also, read the article. Larry hasn’t shown that the rings are older. All he has shown is at the space-weathering evidence may not be reliable. That’s a rather different thing (media hype aside).

    Sad thing is, this rings-researcher actually does think that the rings are old. But I do have to at least acknowledge the legitimacy of the data that suggests the opposite. That’s science rather than ideology.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »