Telesto, Calypso, Polydueces, Helene, & Hyperion discussion

vogon13 · Oct 13, 2005

While posting on Iapetus last night was thinking about a possible escaped satellite it may have had at one time. And then thought of the co-orbital satellites. Cassini has made enough passes thru the Saturn system now that we are starting to accumulate at least distant pictures of many of the satellites. Yesterday, photos of Telesto turned up on the JPL website. Telesto is one of the co-orbital objects that share Tethys' path around Saturn. The other satellite is Calypso. The satellites are in a 'Trojan' relationship with Tethys, they average 60 degrees ahead and behind Tethys as they all go around Saturn. The relationship is stable. Additionally, Polydeuces and Helene are in a similar menage a trois with Dione. Another satellite with a 'relationship' to another object around Saturn, is Hyperion. In the time that Titan orbits Saturn 4 times, Hyperion does it precisely 3 times. This relationship is also stable. I have been curious how so many of these objects wound up in these circumstances. (there are other satellites around Saturn that have similar characteristics) Granted the current relationships, essentially resonant orbits; 1 to 1 and 4 to 3, are stable, but how to contrive so many objects to wind up this way? Just coincidence? Saturn system has much 'clutter', things just sorted out that way. Well, I don't find that terribly satisfying. Maybe there is a mechanism, a subtle 'twist' that makes this sort of thing a little more common than we might suppose. As I was playing around with Iapetus, and a possible lost satellite it might have had long ago, I happened upon a description of a possible tidal mechanism between asteroids and their possible satellites in the book, Introduction to Asteroids, by Clifford Cunningham. Asteroids typically have rotation periods of several hours on up. A possible satellite of an asteroid will interact tidally with the prim <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 14, 2005

you already know what i will say.

vogon13 · Oct 14, 2005

I haven't piqued your interest with tales of moons of moons? Majesty of the clockwork of the heavens and all that. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 14, 2005

yes. that is interesting. absolutely. i believe, too, they have found asteroids that have moons. i like the imagery of the "trojan" formation of the moons orbiting in "packs," with the same orbital period. the reason for this situation would depend on what model you believe is responsible for the formation. and for the possible reason for their groupings. one would have to examine how moons are formed at all, then add constraints to that idea to explain multiples. and then on to groupings that travel together, as if they were one unit. indeed, gravity may capture moons. and moons may capture their own moons. but capture is not the case for every moon. and packs of moons seem even more unlikely to have been captured.

vogon13 · Oct 14, 2005

....moons may capture their own moons.... That is entirely another discussion. This tidal mechanism would be operable to any moon and explains why we do not see moons orbiting other moons (at least moons that are 'primordial' to their respective host body). While it is indeed resonable to suppose such objects never formed (Occam's razor) that there is a 'mechanism' that explains their absence (in orbit around the primary moon) and provides clues as to where they went (Trojan relationship or a resonant independent orbit) and that in fact there are such objects in these relationships consistent with their past origins is quite interesting to me. The possibility of planetary satellites possibly forming concurrently with their own 'secondary satellites' may find further consistency in the ideas that as planets formed around the sun and developed secondary bodies, so to did the secondary bodies. Patterns of nature scaling through a hierarchy of objects, so to speak. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 14, 2005

Let me hasten to add, moons of moons in the outer captured asteroidal populations of Jupiter, Saturn, Uranus, and Neptune are certainly possible and expected. I would suspect their frequency of occurence will be similar to that of the 'parent' population of which they derive. I'm not sure about Saturn, Uranus and Neptune, but Jupiters' outer satellites seem to be spectoscopically similar to Jupiter's Trojan asteroids, and additionally, to the D-type asteroids common in the outer main asteroid belt. Origins of these objects is intentionally not addressed in my posts. But would make an interesting thread {hint!}. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 14, 2005

Curiously, the mass ratio of Titan to Hyperion is not all that different from that of Dione (or Tethys) to any of the 'Trojanettes' and the mass ratio of the planet Saturn to its moon, Titan, is similar in magnitude, also. {sorry, couldn't resist} Note: didn't have mass estimates on the small objects so halved the value for Pandora as a rough (very rough) guesstimate. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 14, 2005

"Origins of these objects is intentionally not addressed in my posts. But would make an interesting thread {hint!}." yes. if we got a model for origins of moons, we may happen upon how such things may cluster, as in a trojan formation, orbiting in the same period, as if they were one entity. in an accretion model, they could have simply locally accreted. the thing is, if accretion is responsible, then why do so many such models result in objects forever colliding, bumping into each other, never to merge? like the asteroid belt. that will never accrete. nor will saturn's ring. or jupiters ring. if anything, these are tenuous structures that will only fade away. however, capture of multiple moons, and then to have them all come into the same rhythm, as one thing, seems less believable.

vogon13 · Oct 14, 2005

Machinations of gravity seem adequate to explain rings of Saturn and asteroid belt. Roche calculated over 100 years ago properties of the region that bears his name, IIRC, Gauss had predicted rings to not be a solid object and his theory was confirmed when the newly invented spectroscope revealed the discontinuous nature of the ring material. In the case of asteroids, again over 100 years ago, Kirkwood noted certain periods of revolution about the sun were curiously absent from the asteroid statistics. Further, he realized these periods bore mathematical relationships to the orbital period of Jupiter. The implications of this are sobering, material across the width of the asteroid belt could have never spread across the 'Kirkwood Gaps' to have ever condensed into a single body. ---Yet--- Kirkwood, Monck, Hirayama (not working together) noted multiple asteroids with similar orbital properties. Further analysis indicates that in some cases, these 'related' asteroids are most likely fragments of parent bodies! Additionally, Gradie and Tedesco, have 'mapped' how the compositions of the asteroids vary with distance from the sun. Again, startling conclusions derive from their work, how else to explain S type asteroids on the inner reaches of the belt, C types through the middle and continuing to the farther edge, and my favorites, the D types starting mid belt and steadily increasing in percentages beyond the far edge of the belt and continuing to the Jupiter Trojans? Materials represent variations in the composition in the nebula the solar system formed from. Asteroids have been studied and increasingly better understood for the last 200+ years, with a great many of the fundamentals having been worked out a century ago. Upsetting established asteroid science and replacing it with something majorly different is neither feasible nor realistic. But their are many fun areas in asteroid (and ring!) res <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 14, 2005

vog, sure. yes. the parent body model for the fragments is more than likely how some of them, at least, came into being. and as well, not every region of the solar system will end up as an accreted planetoid or moon, even if such a process created the ones that did accrete. i'm not here to upset asteroid science. i largely agree with the stuff you are posting. moon formation is still mysterious. and further still is the trojan type of system of moons. they could be explained by having been, as you suggest, one thing fragmented into multiple sections, via some cataclysm, then reconstitued over the eons into spherical shapes due to gravitational forces. if anything, to jump back to asteroids, they may have been once accreted from a larger body that was destroyed, with the varying types of asteroids separating out, as in a centrifuge, according to their characteristic densities and compositions. what, then, are the differing types of asteroids typified by, ie, are they categorized by density? or composition? both? other stuff? you seem keen on that, so i ask the question. i was unaware of that condition. it seems as well that the asteroid belt sort of goes largely ignored as a solar system structure. it's all about mars and comets.

vogon13 · Oct 14, 2005

I have heard the centrifuge thing before and scarcely understand how it can be advocated. Centrifuges work by restraining a mixture and subjecting it to a large rotationally derived force, the materials will sort themselves in response to the pressure gradient. Asteroids are not in any way restrained for this (nonexistent) force to sort them in this manner. I greatly simplified types of asteroids in my post as I wanted to finish typing it up before I go on Social Security. Briefly: S=stony C=carbonaceous D= apparent kerogen on surface, clay and carbon present Q= chondritic? A= apparent olivine material V= Vesta {it and one other 'rock' only known examples} E=plagioclase, fosterite, enstatite composition There are other types too. Catagorization is done by visual and infrared spectroscopy of real asteroids in space with various telescopes and spacecraft, and similar examination of various mineral samples in the laboratory, and by also measuring real meteorites! All these chains of evidence 'hang together' nicely and are mutually reinforcing and consistent. But 'around the edges' there are unknowns and mysteries, and puzzles enough to keep astronomers and amateurs like me busy for centuries. Wait till we start landing asteroid rovers! Something else that is helpful in understanding all these things is how various interactions are expressed (if that's the right word) by different objects around the solar system. That tidally matured multi-asteroid systems may illuminate how Telesto wound up where it is and where it came from is quite fascinating. That aspects of these interactions are observed in the earth-moon system and the Pluto-Charon system is simply amazing. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 15, 2005

vog, thank you for that stuff. it gives me a foundation. the centrifuge thing was the first knee-jerk idea that came to mind. are the different types arranged in compartmentalized zones? or is it largely an aggregate? and if it is stratified, as in layers in terrestrial geology, maybe the structure is like an orbital sedimentary-like deposit matrix. what would be entirely insane is when they do land a rover on an asteroid, that it discovers fossilized organic structures. asteroids could be used as well as semi-permanent outpost sites for communication and monitoring of missions, like interplanetary buoys.

vogon13 · Oct 15, 2005

To be a little more specific (not trying to be a smart aleck here, as this has come up before at SDC) your use of the word organic: {from Random House Websters Dictionary} organic, adj 1. of or noting a class of chemical compounds containing carbon - - OR - - 2. of, characteristic of, or derived from living organisms You see there is quite a difference. Definition 1 has already been demonstrated, (carbonaceous condrite meteorites, and spectroscopic detection of kerogen (or related material) on D-type asteroids among others). Your characterization of 'insane' seems harsh, but I would just say quite unlikely. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 15, 2005

My take on the asteroidal compositional distribution goes like this: Take a sample of 100 asteroids from 10 different regions of the asteroid belt based upon their distance from the sun. Group closest to sun will be so many percent S, so many percent P, etc. As you move outward thru the belt, the relative percentages vary. The gist of this is, a specific asteroid could be found most any where, but the majority of certain types are segregated per distance from sun. The trojan asteroids of Jupiter are almost entirely D, but so is the outer reaches of the asteroid belt, not too much of a stretch of imagination to picture Jupiter 'trojanizing' the nearer available asteroids, but a few 'rocks' of other types have probably 'snuck' in too. That there are occasional 'misplaced' asteroids is not surprising, past collisions can 'caroom' a rock inward or outward. Perturbations of the planets can 'jostle' them too. Compositional analysis of the moons of Saturn by Cassini will be interesting to study, with the example of the asteroid belt, perhaps we can spot trends in the materials around Saturn. If Dione is mostly water ice, and Helene is mostly manganese, the ideas about their past relationship are clearly wrong. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 15, 2005

And had better extend my remarks on the 'Trojanettes' in at least one regard. The possible primordial satellites of these moons that are at a lower altitude, below the level where they would experience the tidal force as raising their orbits, will instead, experience the force as lowering their orbits. This effect is belived to be occuring on Triton now, and would have been operable on these other putative objects too. Obviously, a body at a lower altitude descending will at some point either disrupt or impact the surface. Perhaps we should look for appropriate craters like that, however, they will be among the oldest such craters on the object and will be grossly modified by subsequent impacts and possible geological activity. And an object at precisely the synchronous altitude (thought I'd missed that one too?) will not be expected to survive the life of the solar system, because of the low probability of it forming at that precise altitude, and/or , it would not remain at that point anyhow as the host object's rotation brakes due to the tidal influence of Saturn (in this case) and the 'proper' altitude changes away from where it is. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 15, 2005

Terminology: I am having some confusion in my thoughts about these matters in how to tag these classes of objects so that it is clear to all of us what we are discussing. Having a large planet like Jupiter or Saturn aquiring satellites from the existing solar system population of asteroids results in objects we call moons. Some times (but not consistently by me or others) they are referred to as asteroidal satellites or captured (asteroidal) satellites. This entales (to me anyhow) some confusion in regards to Phobos and Deimos. While 'chunky' in shape and apparently carbonaceously chronditic in their composition, their orbits are quite circular and equatorially aligned. These objects just seem so different from their possible bretheren in the gas giant systems. Objects in a Trojan relationship with a 'bonifide' planet seem to need a handle more fitting their status as not just asteroids, but asteroids in a 1 - 1 resonance with a planet. Objects in a trojan relationship with a moon of a planet need nomenclature different from the planetary trojans. Captured asteroids with satellites (trojan, and orbiting a bonifide planet) need a designator for their satellites. Objects that perhaps someday will be recognized as former 'moons of moons' need a handle too. Objects that are clearly the result of 'fissioning' of a parent body orbiting a planet, like 1980 S-1 and S-3, probably need..... You get the idea. Suggestions? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 15, 2005

what is the synchronous altitude? explain this a bit. are you saying it is already too low, and it's orbit will decay such that the moon will enter the atmosphere of the planet?

bonzelite · Oct 15, 2005

as well, the biggest moons of jupiter particularly seem like planets and not like asteroids at all, as well as titan at saturn --that is basically a planet around a planet. it seems far from an asteroid. what is your take on this?

vogon13 · Oct 15, 2005

I think most agree that upon formation, most (all) major satellites rotate on their axes more than once per orbit around their 'host' (terminology again) planet. Over time, gravitational effects of the host planet 'lock' one side of the satellite facing the host continuously. In the case of the earth and its moon, it seems unlikely that via whatever process the moon formed, upon its formation it was spinning faster than once a month. The earth's gravity over time has arrested this motion. So let's say when the moon formed, it was rotating once every 8 hours (number pulled out of the air, just for example). In that time frame, it would be possible to orbit the moon in 4 hours or 16. In the 4 hour orbit, an extended object like a little asteroid, will experience tidal effects from the moon. It will rapidly wind up rotating in 4 hours and presenting a constant face to our moon. It will also experience a tidal effect that will lower its' orbit, eventually causing it to break up, or clobber the surface of the moon. Our little asteroid in the 16 hour orbit will also adjust its spin so that it keeps a constant face towards the moon. It will also experience a tidal force that will tend to enlarge its orbit. and it will recede from the moon. These effects are analogous to respectively the circumstances of Triton around Neptune (its orbit is decaying, <100,000,000 years, splatto) for the 4 hour example, and earth's moon itself in the case of the 16 hour object. (The earth's moon is receding from the earth a couple of inches per year, at the expense of lengthening the day). I am thinking that a possible satellite of, let's say Dione, at Dione's formation would also be subject to these demonstrated gravitational forces. In a quick low orbit, Dione snarfs the little guy, in a higher orbit, Dione 'repels' the object, but keep in mind, as an object orbits Dione at higher and higher altitudes, Dione's gravitational hold on the object <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 15, 2005

No doubt, Jupiters big 4 moons are large. My fascination with Saturn seems to derive in part from the greater size ranges of the 'mainline' satellites, more modelish of the solar system than Jupiter. As far as I know, 'trojanettes' of let's say Ganymede, don't seem to exist. Haven't thought about why much, I'll put it in the cue. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 15, 2005

how do you think these planet-like moons may have come into being, with such diversity and mass? they're not really asteroid like in any fashion. they are planet-like. i think ganymede is larger than mercury, IIRC.

vogon13 · Oct 15, 2005

Big 4 satellites benefitted in their proximity to Jupiter and snagged some of the 'incoming' for themselves. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Oct 16, 2005

Might have 'fathomed' an earlier post of yours. Let me try wording it thus: Could Dione at some point have captured an asteroidal moon or two, and then 'spun them off' per the tidal interaction to have them wind up in the respective L-4 & 5 locations? Is that maybe the gist of one of your questions? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

bonzelite · Oct 16, 2005

ahhh. i just had an "a-ha" moment. you just said, well, you are mentioning the lagrange positions. this acconts for the trojan formation. we have to come up, as you are doing, with a system to account for those lagrange moons not orbiting the main moon, ie, dione, anymore. this is pretty cool. in this setup, the lagrange moons went from sub-moons, to moons. i'm just trying to visualize the transition from orbiting dione to being fixed in space, relative to dione. hmm. i'm trying to picture the movement, on fast forward, in my mind. it is difficult. they just halted the orbits without drifing in or away from dione. but staying right fixed with it.

vogon13 · Oct 16, 2005

I had posted in another thread that perhaps the crater structures Valhalla and Asgard on Callisto (moon of Jupiter) may be the remains of a co-orbital satellite with its own moon that splattered Callisto long ago. At the time, I hadn't given it a lot of thought but now..... <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

Telesto, Calypso, Polydueces, Helene, & Hyperion discussion

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