Cracking a scientific nut

By Phil Plait | July 17, 2007 6:53 pm

Iapetus is weird. It’s a moon of Saturn, and it’s always been known to be weird. One of Iapetus’s hemispheres is much brighter than the other, for one thing (probably due to collecting material as it orbits the planet). For another, it’s got a pretty big equatorial bulge; it’s not even close to being a sphere. And third, right around its equator, there is this vast ridge of material that’s something like 20 kilometers high!

Yup. It is the walnut of the solar system.

Those two features — the bulge and the ridge — are just crying out that they are related somehow. And now it looks like it may be understood why.

New results just released state that when it was very young, Iapetus rotated very rapidly – something between 5 and 16 hours per rotation. This is what formed the equatorial bulge. But its spin rate now is much longer, about 80 days. Obviously, something in its past slowed the spin.

That something is the immense tidal force of Saturn. This force (really, a product of the gravitational force) can slow the rotation rates of objects. But for Saturn to slow Iapetus, it turns out that there must have been something warming the interior of the little moon when it was very young, and that was found to be radioactive heat. Aluminum-26 and iron-60 are radioactive, and their decay can heat up the surrounding material. Furthermore, they have such short half-lives — meaning they decay away rapidly — that in geological terms it’s as if the heat source switches off.

Now follow this logic: Iapetus spun quickly when it was young, and got the bulge. Its interior was heated by radioactivity. But then that heat source shut down. The moon started to cool, and simultaneously its rotation slowed due to tides from Saturn. When the rotation slowed, the centrifugal force at its equator dropped, and it tried to shrink and resume a spherical shape. But by then the outer crust had frozen. Instead of flowing smoothly into a sphere, the equatorial crust piled up as the Moon shrank, forming the ridge.

Voila. Walnut moon.

Incidentally, because radioactive materials decay at a known rate, and the amount of heating needed to make the theory work implied how much radioactive material Iapetus had, the scientists were able to calculate the age of the moon. The answer? 4.564 billion years, pretty much the known age of the solar system.

Swallow that nut, young Earth creationists!

Speaking of garbage science, I have to mention — regular readers know I can’t help myself sometimes — that Iapetus has long been the target of some, um, nutty ideas. The king of these is of course one Richard Hoagland, who claims that the ridge around Iapetus is artificial. Yes, built by intelligent beings (though as usual he never says who he thinks they are).

You can’t make this stuff up.. oh wait, duh, of course you can. Here’s what he has to say:

[...] it could really be a "wall"… a vast, planet spanning, artificial construct!!

Man, you know this is serious if he uses two exclamation points. I mean, "exclamation points!!" To drive the artificiality point home, he compares the moon to the Death Star from Star Wars in a side-by-side picture — not just once, but twice!

I mean, "twice!!"

He goes on to say:

There is no viable geological model to explain a sixty thousand-foot-high, sixty thousand-foot-wide, four million-foot-long "wall" spanning an entire planetary hemisphere… let alone, located in the precise plane of its equator!

It’s unclear when Hoagland wrote that page, though it’s dated 2005 and there are clues it was in February or March of that year, but at the same time he was feverishly banging away at his keyboard producing that goofiness, a real scientist by the name of Paulo CC Freiere was finishing up an actual paper on the ridge around Iapetus (and you can read a popular-level synopsis of his findings over at Universe Today). In a nutshell (ha! a double pun!) the idea was that Iapetus could have formed that ridge when it slammed into one of Saturn’s rings. The material piled up on the equator, forming that vast range of mountains. That also could explain the difference in brightness of the two hemispheres.

This new idea about Iapetus getting its bulge and ridge by the freezing out and piling up of matter seems more plausible than having the Moon plow into a ring and gathering up matter, but still, we now have two theories on how that structure could have formed. Either or both may turn out to be wrong, but I think the extraterrestrial alien pyramid builders can be dismissed.

Of course, Hoagland continues on his pages to bark on about artificial constructs, doing his usual sleight of hand with over-magnifying images and claiming JPG artifacts are buildings or some such nonsense. And I’ll admit, it’s rather fun to read his stuff, in a schadenfreude kind of way. But in the end, I prefer actual, y’know, science. Speculation is fun, but real science will be more interesting, more exciting, and more satisfying every time.

Comments (56)

  1. You know what else has ridges? Ruffles. My theory is that the entire universe is a gigantic potato chip. This would support your walnut planet theory, as both are snack foods.

  2. Brown

    My first introduction to Iapetus was in 2001: A Space Odyssey (the novel, not the movie). Arthur C. Clarke used a less-common alternative spelling: Japetus.

    This was the place where the second monolith was. The first was on Earth’s Moon; the second was on a moon of Saturn that had one side much shinier than another. The shiny spot acted like a beacon, and when Dave Bowman got close enough to see it, he saw that the shiny spot was round and distinct, like it had been deliberately made that way, so as to have that function. (What function a wall would have is less clear. Perhaps it wasa intended kept out the Mongolians?)

    Clarke’s work was fiction, of course, and he was simply having fanciful fun with the bizarre albedo of Iapetus.

    The reality is even more intriguing than Clarke’s fantastic story.

    Curiously, the prospect of the Earth shrinking as it cools in the future was recently in the news, as reported here (among other places):
    http://www.post-gazette.com/pg/07185/799041-115.stm

  3. Brown

    My first introduction to Iapetus was in 2001: A Space Odyssey (the novel, not the movie). Arthur C. Clarke used a less-common alternative spelling: Japetus.

    This was the place where the second monolith was. The first was on Earth’s Moon; the second was on a moon of Saturn that had one side much shinier than another. The shiny spot acted like a beacon, and when Dave Bowman got close enough to see it, he saw that the shiny spot was round and distinct, like it had been deliberately made that way, so as to have that function. (What function a wall would have is less clear. Perhaps it was intended kept out the Mongolians?)

    Clarke’s work was fiction, of course, and he was simply having fanciful fun with the bizarre albedo of Iapetus.

    The reality is even more intriguing than Clarke’s fantastic story.

    Curiously, the prospect of the Earth shrinking as it cools in the future was recently in the news, as reported here (among other places):
    http://www.post-gazette.com/pg/07185/799041-115.stm

  4. Mark Martin

    We live in a snackiverse.

  5. Brown Says: “My first introduction to Iapetus was in 2001: A Space Odyssey (the novel, not the movie).”

    Mine, too.

    “Arthur C. Clarke used a less-common
    alternative spelling: Japetus.”

    I later found out why he spelled it that way. Using the “J” for iota in the transliteration is a German thing, and he got it from reading Wily Ley’s writings in the ’30s and ’40s.

    “This was the place where the second monolith
    was. The first was on Earth’s Moon; the second
    was on a moon of Saturn that had one side much
    shinier than another. ”

    Actually, the first was on Earth itself, 2 million years ago. The one on the moon was the second one and the one on Iapetus was the third. He goes over all of this in “3001″.

    - Jack

  6. Monkey

    Chris/Mark,
    I agree….but how else, other than an omni-everything creator, do you account for the flavours of this ruffled-snackiverse. Do you think Ketchup AND catsup flavour could evolve into the seemingly same taste?!? And how do you account for dill pickle?

    Just to be obvious…this is a joke. Happy trails, folks.

  7. The BA says: “To drive the artificiality point home, he compares the moon to the Death Star from Star Wars in a side-by-side picture — not just once, but twice!”

    He’s obviously all wrong. Iapetus is not the Death Star, Mimas is:

    http://www.astro.virginia.edu/class/skrutskie/images/saturn_mimas_death.gif

    - Jack

  8. Mark Martin

    Indeed, there is even a serving of 2% milk spilled carelessly across the sky. And the Moon? It’s made of CHEESE. We are on the verge of a new unified-snack-field theory.

  9. ABR

    I thought the equatorial ridge was the seam leftover from the mold during casting of Iapetus!

    Regarding the numbering of monoliths…good catch, Jack — you beat me to the punch. I still think it’s cool that there are people making the distinction between Jupiter system (movie) vs. Saturn (book).

  10. Troy

    Iapetus is a very interesting moon. This is the first I’ve heard of the rapid spin/contract theory. It seems quite plausible. You (the BA) always seem satisfied when presenting information that contradicts young earth creationism, yet the most blatantly satisfying and easily understood refutation is that objects millions (and billions) of light years away would have to be ahem ‘created’ with the light all ready on the way.

  11. BA wrote:
    “Incidentally, because radioactive materials decay at a known rate, and the amount of heating needed to make the theory work implied how much radioactive material Iapetus had, the scientists were able to calculate the age of the moon. The answer? 4.564 billion years, pretty much the known age of the solar system.”
    This is pretty much the same thing said in the linked Cassini article:
    “The heat source had to have a limited life span, to allow the moon’s crust to rapidly become cold and retain its immature shape. After looking at several models, scientists concluded that the heat came from its rocks, which contain short-lived radioactive isotopes aluminum-26 and iron-60 (which decay very rapidly on a geologic timescale). Since these elements decay at a known rate, this allowed scientists to “carbon date” Iapetus by using aluminum-26 instead of carbon. Scientists calculate the age of Iapetus to be roughly 4.564 billion years old.”

    So my question/comment is: Which came first? Information that these isotopes were present on Iapetus in some ratio (and back extrapolating to ratios early in Iapetus’ existence), or that the short term heating needed to be explained and a particular mixture of isotopes matches that? Hopefully there is some other method which lead to the model, as either of the above would require some assumption for the life of the moon (meaning age would be an input… not an output). What am I missing? Is the current spin rate and theoretical early spin rate the missing extra variable?

  12. Keith Harwood

    Nah, they are all wrong. That ridge, it’s a mould mark. They just forgot to grind it off before they put the moon in place. Sloppy workmanship, that’s all.

  13. Chris, from what I understand, they calculated the needed amounts of the isotopes knowing the heat generated and the heat needed, and from that you can work backwards to get the age of the moon.

  14. Chill Out

    I was a little confused by the article when you made this statement: “But for Saturn to slow Iapetus, it turns out that there must have been something warming the interior of the little moon when it was very young.” Theres no connection between the heat of a body and the effect of a gravitational tidal force upon that object right? So why are they connected in regards to the ridge?

    Do you mean that in order for a ridge to form there must have been heat and then suddenly not? That would make more sense to me within the context of the next part about the radioactivity in the core.

  15. When I first saw it, I thought that if someone had made that as a visual effect for a movie, people would be crying, “How fake! You can see the seam where he put the molds together! No moon would look like that!” And yet, here one is.

    The Universe always gives us something weird. That’s why I love it so!

  16. blizno

    Chill Out, I believe the importance of heat is that the core of the moon was molten when it was spinning faster because of the radioactive materials heating the core. When the radioactive materials lost enough power, the moon began to freeze, rather rapidly in the scale of the solar system, while the moon was slowing its rotation because of tidal effects. As the moon began to freeze, and was slowing down at the same time, the freezing crust at the equator stayed in roughly the shape it held while the moon was spinning faster but the rest of the moon “subsided” into a more spherical shape before freezing solid.
    This wouldn’t have happened all at once. The outer edge of the ridge would have been barely above the surface at the start of the process and the non-ridge surface would have slowly pulled away from the ridge as the moon slowed its rotation and became rounder. That would lead to the lovely shape of the sides of the ridge.

  17. If there’s another picture and “MYSTERY SCIENCE THEATER 3000″ is on the other side…..

    J/P=?

  18. wright

    Even more evidence that our own little backyard in the universe is chock-full of wonders. We are just scratching the surface (literally) of what the other bodies of the solar system have to tell us. What a great time to live in.

  19. TheBlackCat

    I think the reason the molten core is important is that the moon has to change shape in some way for there to be any “tides”. If the moon isn’t changing shape then it isn’t bleeding off any energy and thus its rotation speed is not changing.

    And wouldn’t they have a pretty good idea about what radioisotope ratios would be present by looking at the decay products in meteorites and such?

  20. DrKC

    I think chris is on to something important here, comming up with 4.564Gy using a geologic model heated by aluminum26 and iron60 really smacks of fitting numbers to the observed instead of observing the numbers, on the other hand, the model itself sounds very reasonable to me, as a geologist, and being so, I volunteer myself to fly out and get samples to test for the proper daughter products, anyone willing to finance the project? (nudge Bill Gates).

  21. I have not read the scientific paper (yet), so I am a bit unclear on the details of the model. They claim the temperature of the core affects the way tidal energy is dissipated in the moon, and in qualitative terms that makes sense to me. That’s why they can assume an amount of radioactives in it. But to get the numbers to balance out correctly, they assume an abundance of the isotopes. However, when you calculate the moon’s age based on that, it comes out to be the same as the age of the solar system. That sounds like an independent check. I’m going to try to read the paper soon.

  22. scienceteacherinexile

    Hoagland is still around? er… I mean Hoagland is still around??
    The only time I hear about him is here (and occasionally other science blogs).
    I read a lot of his crap about Mars, but tired of it quickly since it was like reading bad comedy.
    But how much cash has he made selling this crap as science? If I had less integrity, I think I would take a shot at making bizarre claims, packaging them as science, and see if I could sell a few books. It must be easier when you get to make it up instead of doing actual research.
    By the way, Hoagland seems to insinuate that the ridge it artificial because the moon resembles the Death Star…. Does he know that the Death Star is not real?

  23. Exodust

    You know what you can tell that Richard Hoagland guy, that extraordinary claims require extraordinary proof. So tell him to stick his theory up his (insert an anatomical place here)…

  24. Crux Australis

    OMG what a nutjob (pun intended) Hoagland is. Can anyone explain what “zero-gravity crystalline titanium” is? I’m guessing not. I kind of stopped reading after that, but I was intrigued by what he calls buildings. Maybe my screen is set to show reality; I don’t see anything like buildings, nor even the square craters he babbles about. Yikes.

  25. Bigfoot

    Does nobody else realize what a golden opportunity this is? NASA should be building the world’s (solar system’s ?) largest nutcracker right now. At last, our first chance to crack open and stare directly into the heart of a spherical body in space. Of course, they should be extremely careful, though; we don’t want to crumble the meat inside!

  26. Nick

    There is one thing I will give Hoagland credit for: he wrote an article or paper or something-or-other about Europa (about how it may have liquid water and could support life) which was one of the inspirations for Arthur C Clarke’s book 2010: Odyssey Two, one of my favourite books. Otherwise, he’s a total nutjob.

  27. JC

    Richard Hoagland…. well thanks BA, for that link. Next time I need a sanity check, I will read his work to give me a control on what crazy REALLY is…

  28. Luke

    To paraphrase Terry Pratchett, multiple punctuation marks are a sign of a diseased mind.

  29. Sergeant Zim

    It’s a beautiful day when you can heap scorn on not one, but TWO classes of woo in the same post!
    Dr. BA, kudos to you, keep on holding the figurative feet of the woomeisters to the fire, and demanding evidence from them, while simultaneously providing it ofr reality.

  30. Mr. Del

    > “That something is the immense tidal force of Saturn. This force (really, a product of the gravitational force)”

    Tsk, tsk. It’s a *derivative* of the gravitational force.

  31. Irishman

    Following the first link to the Iapetus results, I see this:

    Scientists calculate Iapetus originally rotated much faster — at least five hours, but less than 16 hours per revolution.

    Five hours per revolution is faster than 16 hours per revolution. That is because it is a period, which is an inverse. They think they’re talking about frequency, how many turns per unit time.

    Something can’t spin faster than 1/5 revs per hour (0.00333 rpm) and simultaneously spin slower than 1/16 revs per hour (.00104 rpm).

    The heat source had to have a limited life span, to allow the moon’s crust to rapidly become cold and retain its immature shape. After looking at several models, scientists concluded that the heat came from its rocks, which contain short-lived radioactive isotopes aluminum-26 and iron-60 (which decay very rapidly on a geologic timescale). Since these elements decay at a known rate, this allowed scientists to “carbon date” Iapetus by using aluminum-26 instead of carbon. Scientists calculate the age of Iapetus to be roughly 4.564 billion years old.

    After looking at several models? What other models were considered? What lead to selecting radioisotopes over the other models? What lead to selecting these radioisotopes?

    Troy said:
    > You (the BA) always seem satisfied when presenting information that contradicts young earth creationism, yet the most blatantly satisfying and easily understood refutation is that objects millions (and billions) of light years away would have to be ahem ‘created’ with the light all ready on the way.

    In this case, you would have to state that the universe (and Iapetus) was created with age. That doesn’t just mean light on the way, but radioactive decay results in place, weathering, etc. That requires a trickster God, someone who wants to mislead his people. Not exactly a trait consistent with a loving, all-good God, but hey, once you throw out logic, reasoning, and consistency, anything goes.

    TheBlackCat said:
    > I think the reason the molten core is important is that the moon has to change shape in some way for there to be any “tides”. If the moon isn’t changing shape then it isn’t bleeding off any energy and thus its rotation speed is not changing.

    Even solid rock is affected by tides.
    http://www.badastronomy.com/bad/misc/tides.html

    scienceteacherinexile said:
    > By the way, Hoagland seems to insinuate that the ridge it artificial because the moon resembles the Death Star…. Does he know that the Death Star is not real?

    Hoagland seems to think that fictional creations are secret insights into the hyperdimensional reality. Lucas was apparently a seer, a channeler of mystical information. Or soemthing equally as stupid.

  32. jotetamu

    How did they support the idea of using iron-60 and aluminium-26? Is there any evidence that these were suitably abundant in the early solar system? If they just tweaked the amount and timing of heat needed in their model to make Iapetus come out right, then looked around for isotopes with halflifes that would give them that, then without independent reasons for supposing that those isotopes were present it doesn’t seem very convincing.

    I hope BA or some other blogger takes the trouble to explain the paper to us lazy laypeople, because it does seem a neat idea. (BA said in a comment that he hasn’t read the original paper yet.)

    Jim Roberts

  33. Is there a planet, moon or feature in the Solar System that Hoagland thinks is natural?

  34. Phil,

    Great post!! I wanted to point out another analogy to Hoagland’s claims. He is, in fact, making an Intelligent Design (ID) claim. His logic is the same as ID – we have no naturalistic explanation for the ridge, therefore it was intelligently designed. This case shows the inherent weakness of making such an argument from ignorance. Give scientists time, they will find an explanation. Even if they don’t what you have is a mystery – an unknown – not a known alien artifact. Concluding it’s alien would require some positive evidence of artifice, which is lacking.

  35. Quiet_Desperation

    I have to say, though, that there is a part of me that really *wants* it to be a derelict spacecraft. :)

    >>> To paraphrase Terry Pratchett, multiple punctuation
    >>> marks are a sign of a diseased mind.

    Nonsense!!! :)

    I love me some Pratchett, but there are, IMHO, times when a “?!” is valid.

    That would be “!?” for those of you south of the equator.

  36. Go to the Cassini article and you will see one of the authors is called Castillo. Google Scholar ‘Castillo Iapetus’ and the second hit is this.

    Although it’s nearly two years old it seems to be essentially the same information (though the numbers are slightly different). Although the abstract is hard to follow, as I understand it they are saying that they can use the shape of Iapetus to deduce the amount and approximate timing of energy release to soften Iapetus enough for Saturn’s tidal force to affect it at the right rate. The timescale points to Al26 (which is already known to have existed in the early solar system because its decay product Mg26 is found in meteorites) as the culprit (and since then they have thought of Fe60, presumably).

    The crucial point for the age of Iapetus seems to be that they can deduce the amount of these isotopes in the newly-formed Iapetus. They also know the amount that existed at the time meteoritic Calcium-Aluminium inclusions (that’s the CAIs of the link there – CAIs are thought to be the oldest solid objects that formed in the solar system) formed, and the difference allows them to work out how much younger Iapetus is (about a million years in the link, seemingly revised upwards somewhat now) than the CAIs, which can be dated from other, long-lived isotopes.

    So I think Rich is right – it isn’t an independent check on the age of the solar system, because it depends on knowing the age of the CAIs. Indeed, if this work had led to an independent measurement of the solar system, I think that would probably have been the main headline.

    I love this kind of chain of reasoning, though, the way they can deduce so much from aparently so little. Fully deserving of some extra exclamation marks. You might like to spare a bit of awe for Google, too.

    I assume that the linked abstract is for preliminary results at a conference and this is now the finished paper.

  37. Gah, that link doesn’t work. Try http://tinyurl.com/2mravu

    D

  38. CR

    Hoagland thinks that an old ViewMaster set of Tom Corbett: Space Cadet is actually NASA whistleblowers revealling a real key to some long-lost extraterrestrial civilization. I probably read about that somewhere hear at BABlog or in the BA Hoagland entries. In any event, I actually have that old ViewMaster set! (!!)

    Oh, several people beat me to it, but it’s Mimas that more closely resembles the Death Star. Even has a superlaser dish on it.

  39. MattFunke

    Irishman: Following the first link to the Iapetus results, I see this:

    Scientists calculate Iapetus originally rotated much faster — at least five hours, but less than 16 hours per revolution.

    Five hours per revolution is faster than 16 hours per revolution. That is because it is a period, which is an inverse. They think they’re talking about frequency, how many turns per unit time.

    You’re absolutely right about revolutions and periods and frequency, but I think you misunderstand the article. The article means that Iapetus originally rotated much faster than it does now. Each revolution took, at the least, five hours, but less than sixteen hours. Nothing there says that they believe five hours per revolution is slower than sixteen hours per revolution.

  40. Eric

    that’s no moon…
    …it’s a spacestation

  41. Dear Bad Astronomy

    I am writing to support your endeavour. I am a big fan of your site, it is much needed in an age where the Internet makes it so much easier to spread lies and misinformation.
    I am the scientist who proposed the theory that Iapetus might have collided with a ring of Saturn. I have submitted that paper for publication in the Journal of Geophysical research, but it was rejected. The referee had very good points on why the theory was improbable, and that impression has been reinforced by some subsequent talks I had with the planetary scientists at Cornell University. It is very unlikely, from a probabilistic point of view, to have the orbit of Iapetus exactly aligned with the equator of Saturn, to the point that all particles in the saturn ring will hit the Iapetan equator, no to mention the required orbital migration. So, basically, their arguments convinced me that my hypothesis was not likely to be a good description of what really happened.
    However, I don’t think it was entirely wrong… Recently, Wing Ip has proposed that the equatorial ridge might be the result of the collapse of a former ring of Iapetus, such a ring could have formed naturally form impact debris in orbit around this satellite. The equatorial oblateness of Iapetus would insure that all orbiting debris would form a ring. There is nothing improbable about his hypothesis, although it raises the question of why don’t we see such structures around other moons. Because it is a much better hypothesis, his idea was published in October 2006 by the same journal that rejected my paper (see Geophys. Res. Lett. 33, L16203, 2006).
    I guess I was a bit embarrassed about proposing such an implausible hypothesis, a bit more study and work would have shown that. But that hypothesis had some hint of the truth, the action of a ring. This is how science progresses. People propose explanations, is they are not statistically plausible, or if they don’t match observations, or are physically impossible, the explanation is rejected, and we search for a better one. One thing is clear to me: after Wing Ip’s paper, it is clear to me that we could form something like the equatorial ridge of Iapetus without having to resort to pyramid builders!!!

    Keep the great work,

    Paulo Freire
    Arecibo Observatory / Cornell University

  42. Irishman

    MattFunke, my point is that the garbled wording creates a semantic mess. You would not say that “that was at least 1/2 but less than 1/4″. It does not make sense. The association of maximum and minimum is reversed. It only looks right because 16 is greater than 5.

    Rephrasing it to say “from 5 to 16 hours per revolution” would have been better.

  43. MattFunke

    Irishman: my point is that the garbled wording creates a semantic mess. You would not say that “that was at least 1/2 but less than 1/4″.

    Because 1/4 is less than 1/2. I would say that something (whatever you might care to name) was at least 1/4 but less than 1/2.

    Irishman: It does not make sense. The association of maximum and minimum is reversed. It only looks right because 16 is greater than 5.

    I agree that it makes a semantic mess and that they could have phrased it better. I don’t believe that they were mistaken in what they said, however, which is what you originally asserted.

    The article is stating that the smallest amount of time a rotation would have taken (at least) is five hours. In any event, the amount of time a rotation took is less than 16 hours.

  44. K27

    How is the “scientific” explanation more exciting or more interesting in any way? Alien artificial constructs and death stars are way more exciting than, accidentally forming a ridge when it hit Saturns rings…..boring. I think our very own moon is a hollowed out space ship, what do you think of that? Do some research on the moon, google it bitches!

  45. YEC

    The response is very simple (to wit, from Creation Safaris [www.crev.info]):

    As to the “roughly 4.652 billion years” figure, that is ridiculous. What did they expect, the exact month and year? There’s no way the evidence from Iapetus can yield a date to four significant figures without assuming the very thing they ought to be proving. Dates are inextricably linked to the assumptions made. Those assumptions should have been stated up front. They have blindly accepted a consensus date from uniformitarian, evolutionary theories, and molded their data to fit it. Yet they spoke of these dates as facts.

  46. Irishman

    YEC, that response is funny. 4.652 billion years is 4,652,000,000 years. That gives, oh a million years of leeway there. Not exactly month and year, is it? Plus, the number in the article above is 4.564 billion years.

    MattFunke said:
    The article is stating that the smallest amount of time a rotation would have taken (at least) is five hours. In any event, the amount of time a rotation took is less than 16 hours.

    I agree that is what they are trying to convey. My original wording is an attempt to describe why that wording fails, why it is semantically bungled.

    In the context of the original sentence, “at least” implies a minimum. But in fact, 5 hours per revolution is the fastest speed. 16 hours per revolution is slower. It is the juxtaposition of “at least” with the fastest speed that is the issue. I realize 5 is less than 16, but the construction of the sentence is crappy. It should have been stated differently.

  47. Irishman

    bungled coding. Take 2:

    YEC, that response is funny. 4.652 billion years is 4,652,000,000 years. That gives, oh a million years of leeway there. Not exactly month and year, is it? Plus, the number in the article above is 4.564 billion years.

    MattFunke said:
    > The article is stating that the smallest amount of time a rotation would have taken (at least) is five hours. In any event, the amount of time a rotation took is less than 16 hours.

    I agree that is what they are trying to convey. My original wording is an attempt to describe why that wording fails, why it is semantically bungled.

    In the context of the original sentence, “at least” implies a minimum. But in fact, 5 hours per revolution is the fastest speed. 16 hours per revolution is slower. It is the juxtaposition of “at least” with the fastest speed that is the issue. I realize 5 is less than 16, but the construction of the sentence is crappy. It should have been stated differently.

  48. Irishman

    Chris said:
    > So my question/comment is: Which came first? Information that these isotopes were present on Iapetus in some ratio (and back extrapolating to ratios early in Iapetus’ existence), or that the short term heating needed to be explained and a particular mixture of isotopes matches that? Hopefully there is some other method which lead to the model, as either of the above would require some assumption for the life of the moon (meaning age would be an input… not an output). What am I missing? Is the current spin rate and theoretical early spin rate the missing extra variable?

    Chill Out said:
    > Theres no connection between the heat of a body and the effect of a gravitational tidal force upon that object right? So why are they connected in regards to the ridge?

    jotetamu said:
    > How did they support the idea of using iron-60 and aluminium-26? Is there any evidence that these were suitably abundant in the early solar system?

    Haven’t had the chance to read the paper. This is the chain of reasoning I’ve been able to piece together.

    —–
    Iapetus has a bulge not consistent with current rotation rate, and an equatorial ridge. If Iapetus had spun faster when young, it would have been shaped to fit the bulge. The only reasonable means for Iapetus to have slowed from that speed to the current speed is tidal interactions with Saturn.

    Calculations for tidal slowing would not fit the speed differentials in the time frame if Iapetus had been solid. However, a liquid or semi-liquid (mixed state) planet would have higher tidal reactions, and slow more. But Iapetus is not currently liquid or semi-liquid. In order to be in that state, Iapetus would need more heat. But that heat would need to have been present for the slowing, then disappear before the present.

    A number of heat source models were evaluated, including decay of long-lived radiogenics, different surface properties (greenhousing, low emissivity, insulating layer), and impact heating. None of those was sufficient to account for the heating except the long-lived isotopes, and they would still be around. But short-lived isotopes could account for the heating, and would be gone.

    There appear to be “Calcium-Aluminum-Inclusions” (CAIs), which contain aluminum-26. Meteorites from the inner solar system have been found with aluminum-26 and iron-60. Therefore, these are likely candidates. Calculations using these decay rates set the age of formation to an approx. 2 Million year tolerance band.

    Furthermore, a hot Iapetus would shrink as it cooled. The solid crust over liquid interior would freeze the crustal bulge for the faster rotation speed, so it would retain the basic shape, and the shrinking caused by the cooling would require the matter to go somewhere, so it piled up around the equator.

    Ergo, squashed shape not fitting current speed and a ridge around the equator. And an approximate age for Iapetus, to boot.

  49. KenW

    Another thing to note about Iapetus is that of all the roughly spherical (that is, larger than asteroidal rock chunks), regular satellites of the gas giants in our solar system, Iapetus has *by far* the most distant orbit, the longest rotational period, and, by implication, the lowest gravitational acceleration by its primary.

    In the Saturnian system, if you omit Titan (which is much much bigger, and in a class by its own), Iapetus and Rhea are roughly comparable, with Rhea a little bit bigger and more massive than Iapetus. But Iapetus orbits 7 times further away from Saturn than Rhea, and its orbital period is almost 18 times longer.

    If you assume that *all* of the gas giant major satellites were essentially melted down during the first couple million years of the solar system as a result of the radioactive heating due to the short-lived radioisotopes, Al26 and Fe60 — a fair assumption since a good portion of the asteroids did the same during this period, and those were mostly much smaller bodies — then all of them (at least ones the size of Mimas or bigger) would have relaxed into oblate spheroids consistent with their rotational periods and self-gravity early on.

    Now other things being equal, in a given system, the smaller moons would have frozen up faster. But in a given system, the tidal effects that drive a satellite into synchronous rotation with its parent body are significantly greater the closer the moon is to its parent.

    So of all the regular moons of the gas giants in our solar system, what is the best single candidate for freezing up sufficiently quickly after the initial million or two million year heating pulse so as to develop a rigid outer shell that could resist gravitational relaxing *faster* than that moon was slowed into synchronous rotation by tidal action? Yep, Iapetus.

  50. Adam

    Phil, you say that “Speculation is fun, but real science will be more interesting, more exciting, and more satisfying every time.”

    I fail to see how the “real science” attached to the explaination of Iapetus’s features is anything other than speculation.

    If you are a real believer of science, then you know that practically all of science is just speculation and best guesses.

    Naturally some are more likely than others, and Hoagland’s claim is particular far fetched, but the scientific explainations are pretty far fetched too in my opinion. They make claims that “Iapetus has such-and-such rotation and such-and-such internal heating” when they do not know these things.

    At least Hoagland claims that it ‘could’ be this or that instead of saying that it IS something that the person actually does not know.

    badastronomy is a pretty good name for this site…

  51. BDW (Baum Des Wissens)

    Adam,
    I find your reply to Phil to be very insightful. It intrigues me how the malcontents of the once status quo (i.e. Creationism, Intelligent Design, Judeo-Christianity, etc.) will rally about an unpopular theory in the 19th century then magically evolve it into mainstream scientific dogma or techno-religion within a century or so. Its fascinating how small inaccuracies about radioactive decay, radioisotope dating, and other ‘guesstimates’ of science are somehow raised to lofty levels of factuality simply by some Darwinist atheist techno-guru saying it is so to the masses.

    Oh they do a fair job with the spin-control on Fundamentalist’s basic misinterpretations of Moses’ words about our arguable ‘creation’ origins. They use abject ridicule like a broad-sword to smite the old-school thinking bible thumpers as if it was some sign of high intellect and not just high school bully tactics.

    I find it difficult to understand why people like Phil can not keep an open-mind to alternative theories to his form of religion. Science today is a religion. Believe it or not there is a hard scientific angle to the bible record too. Its just that the Fundamentalists are not equipped for the task. They are like children who lack understanding. Of course the Earth is billions of years old. Of course Iapetus may be too. By all “known” data about the metaphysical supernatural beings (aka God’s spiritual sons?) they too are billions of years old too.

    So just maybe the “ET” life that Hoagland and others are referring to are in fact THEM and not the fantastical beings you refuse to believe could ever exist. Darwinism is illogical as it does not take into account a grand supernatural architect. Logic would dictate that our existence is far too complex for random chaotic origins and slow evolutionary changing from Simians to humans who can land a space ship on the Martian north pole just yesterday. That’s a “no brainer”!

    Hoagland in my humble opinion is a complicated man. He is conflicted between Creationism and Darwinism. I believe he has low self esteem issues as he feels he needs to fabricated biographical data about his past. He is not a NASA engineer. He was never curator at the Quadrangle in Springfield, MA, and he never produced a radio program in Hartford CT. I know as I live there. Walter Cronkite thinks he’s a “kook”.

    But Hoagland’s theories have merit. Don’t reject them so quickly. Remember the late Arthur C. Clarke was right about things you use and take for granted everyday – satellites!

    Hoagland may be a bit undereducated and unrefined in his speaking style. He may jump to conclusions without explaining his theories (i.e. hyper-dimensional energy?) but don’t throw out the baby with the bath water just yet. His theories about Mars and artificiality may prove quite amazing to you soon enough. Remember Percival Lowell, Giovanni Virginio Schiaparelli, and the Royal British Academy were all doing similar prognostications during the last turn of the century but were shouted down by the ridicule of the anti-ID masses of the day.

    Iapetus’ ridge may be artificial IMHO. But not based on what Hoagland says. It could be related to something else equally as baffling (arguable as nutty) as his theory.

    Just my POV…

    BDW

  52. BDW (Baum Des Wissens)

    Oh and I forgot to mention that Arthur C. Clarke KNEW about the Cydonian ‘face’ long BEFORE the alleged NASA discovery. How could that be? Food for thought that all that glitters is not gold (replace gold with your ilk’s specious origin theories Phil).

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