Telesto, Calypso, Polydueces, Helene, & Hyperion discussion

[bonzelite]

that is a good point. <br /><br />so, then, this may be a stretch, but would you consider any of the moons of jupiter or saturn to be captured planets? <br /><br />i'm still thinking about the fixed lagrange positioning from a prior orbital path. the orbit, then, would "decay" to the point where it would simply STOP and get parked at the lagrange point. the moons orbital period would go from tidally locked, moving ever slower than the parent body, to totally stopping and parking. that is tripped out!!

 

[mikeemmert]

If you are looking for crashed Trojan moons, look at Uranus' moon, Miranda. The two "racetracks" are, in my opinion, the impact site for Miranda's Trojan moons:<br /><br />http://seds.lpl.arizona.edu/billa/tnp/miranda.html<br /><br />When I saw those, I predicted in a letter to JPL that similar features would be seen when Voyager arrived at Neptune. Sure enough, check out Neptune's moon, Proteus:<br /><br />http://seds.lpl.arizona.edu/billa/tnp/proteus.html<br /><br />Looks like the Lagrange points aren't so stable after all. I think the Sun/Neptune Lagrange points yeilded Pluto, Triton, Xena, and 2003 EL61.<br /><br />To see how Triton got captured into it's strange orbit around Neptune, see my GravitySimulation:<br /><br />http://orbitsimulator.com/gravity/simulations/XGorilla%201.1.gsim<br /><br />I think the escaped object is Xena.<br /><br />

 

[vogon13]

Seems the gist of some of this is that there are possibly three methods of putting material into an L4 or L5 position. It can form there 'primordially', it can drift in from the neighboring asteroidal population, or (speculation here) a 'sub moon' can be 'spun off' by a moon and if conditions are favorable, the object can 'drift on over'.<br /><br />Had occured to me, earth's moon is in an advanced state of approaching this condition, in that tidal recession has already 'lofted' it to an altitude above earth where it's gravatational interaction with the sun is now roughly twice that it has with earth. The rate at which the moon is still receding (sadly for the fun of watching its eventual disposition) though, in this epoch, is such that the 'final outcome' will take longer than the age of the solar system.<br /><br />I am also wondering about a relationship between the mass ratio and seperation distance of a binary asteroid and how closely that system could approach Jupiter or Saturn with out disrupting the binary relationship.<br /><br />At first thought, it would seem binary asteroids could transit the Saturn system , for instance, and as long as they did not pass near the Roche limit, they would remain paired. But, as I recall, Roche considered objects in orbit. This binary asteroid scenario could occur for objects in a hyperbolic path, and I am not sure if that is addressed by Roches' ideas or not.<br /><br />Seems like some orbit sims would help here....<br /><br />{hint!}<br /><br /><br /><img src="/images/icons/smile.gif" /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

Let my try some 'guided mental imagery':<br /><br />Picture a rock in orbit around Dione. It slowly spirals up and away from Dione. As it climbs, the rate of climb is actually quite low (as such things go).<br /><br />Also, as the 'rock' climbs, Dione's gravitational pull weakens with distance. As Dione orbits around Saturn, and the rock is spiralling away from Dione, Saturns' gravity will remain essentially constant. Gradually, you will note the attraction between Dione and the rock is overtaken by that between Saturn and the rock. The process is actually quite gentle, and the rock slowly 'wafts' away from Dione. Since the force moving the rock away from Dione is so gentle, the rock winds up in an orbit around Saturn scarcely different from that of Dione. If there is any 'favored' locale along that orbital track, a divot, if you will, the rock will gently settle into it.<br /><br />These divots are the L4 and L5 positions, 60 degrees ahead and behind Dione in its track around Saturn.<br /><br />I envision this process as taking quite a while. (some one else can do the math, I'm allergic)<br /><br />The relative velocities involved are small, and what the heck, we have eons to complete the manuever.<br /><br />That Tethys and Dione have such objects, and perhaps Hyperion is related too, is perhaps suggestive of a mechanism like this to emplace the 'rocks' accordingly.<br /><br /><br />Note: It appears Mimas may have a LaGrangian object too. Considering the possibility that Mimas may have disrupted and reformed at least once, perhaps a second mechanism (Mimas missed a piece during the re-accretion phase) can place material in an L4 or L5 position too.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

To revise and extend my last post:<br /><br />As the 'rock' spirals outward from (in this example) Dione its' orbital period around Dione lengthens. Lets say the rock starts out in an 8 hour orbit around Dione. Recall that Dione takes roughly 64 hours to go around Saturn. So the rock will make 8 'loops' around Dione for every 'loop' Dione makes around Saturn.<br /><br />As the rock rises (from the tidal interactions described earlier) the number of 'loops' (orbits) the rock makes around Dione per each of Diones orbits around Saturn decreases. With the rock at an altitude above Dione to take 16 hours for an orbit, only 4 'loops' can be made for each trip around Saturn.<br /><br />If you plot this out, you will note that as the number of orbits around Dione decreases per orbit around Saturn, that when the 'rock' crosses Diones' orbital path, it describes a shallower and shallower angle at the crossing point.<br /><br />It's as though (from this viewpoint at least) the orbit of the 'rock' 'relaxes' from going around Dione, and stabilizes (or approximates) closer and closer to the path that Dione itself takes around Saturn.<br /><br />One might think that as a satellite orbits higher around Dione, that the 'gyrations' relative to Saturn would grow larger, but actually, the intensity of the 'undulation' decreases. The satellite of Dione 'eases' into a path around Saturn scarcely different from the path of Dione around Saturn.<br /><br />This may also illuminate how Hyperion wound up where it did. Due to Titan's much greater mass, the gentle 'gyrations' and 'undulations' of Hyperions possible orbit around Titan would not have been so gentle. Titan would have retained a grip on Hyperion to a far greater altitude above Titan than any other satellite interior to Titan could have. <br /><br />Additionally, NASA results regarding other solar system objects shows (in regards to smaller, non consolidated objects) a surprising resilience to impact damage. Indeed, Hyperion bears enorm <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[jmilsom]

This image was posted by Andrew Brown (3488) on the Cassini update thread a couple of weeks ago. I thought I would post it here with a question:<br /><br />I find these images amazing. Helene looks like it has had a really rough time (and that may support some of your ideas above Vogon). What processes do you think leads to Helene being so beaten up? I realise Dione's trojan is only 32km in diameter, but look at the size of that feature on the near side? How tall do you figure that to be?<br /><br />Image Credit: <br />NASA/JPL/Space Science Institute <div class="Discussion_UserSignature"> </div>

 

[vogon13]

Maybe Helene is a coallesced object?<br /><br />Might be 3 or 4 smaller 'blobs' jammed together. Nice view of the cleavage (if that is what it is).<br /><br />One of the Trojanettes (Telesto?) is quite smooth, too. Not sure where that leaves us regarding the tidally evolved moonlets of satellites thing. . . . . .<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[vogon13]

bump<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>