On a ring origin of the equatorial ridge of Iapetus Options

[Guest_AlexBlackwell_*]

Wing Ip just had an interesting Iapetus-related paper published in GRL.

[tasp]

Of course, the most interesting bit of the ridge system (the highest parts) are right at the limb of the existing Cassini images. And there is a tremendous amount of subsequent cratering damage all along the ridge structure.

(oh, to have seen it shiny and new . . . . )


That the highest end is discontinuous is a concern. More cratering damage? Perhaps subsidence of the crust beneath, or collapse of the steeper walls occured.

More pictures are needed. And hopefully we get them in 2007.


Additionally, imagine with the minds eye if you will, the lowest edge of the ring, contacting the very highest spot along the Iapetan equator. As the chunks and particles impact the pinnacle, there will be a spray of pulverized ring material released at the contact point. Any material directed upward will interact (ie. decelerate) any material still orbiting in the ring system above the contact point at that instant.

Some of that material will fall to the surface, downrange of the contact point. Some of that material, even though very slightly decelerated, will still manage to complete one more orbit and return to the contact point.

Some of the material, though, will be decelerated into an orbit that is now eliptical. Depending on how close to the surface such doomed ring particles get, they may intercept other high spots along the ground track and accumulate. The lowest objects may get snagged quite aways around Iapetus, where as a particle in a slightly higher orbit might clear that obstruction, and nail another further along.

I think the ring system can emplace at a main primary point along the equator, but there could be a small percentage of materials that may accumulate almost all the way around Iapetus at more than one other secondary location.

Note, the majority of the materials decelerated by the spray above the conact point will fall to the surface along the ground track up to 90 degrees around from the highest spot along the ridge, and this is why the ridge smoothly slope downward from the high spot. Even the 2 nonparallel diverging ridge attendent structures do so.


If one could look down upon either pole of Iapetus and see the silhouette of the equator, the highest heights would all approximately describe an ellipse of elevations around Iapetus.

We also would not expect to see ring material deposits in large deep basins (such as the famous landside basin photographed by Cassini earlier in the mission), there being no eliptical path from the contact pinnacle to the floor of the basin that does not intersect an obstruction along the way. Where the ridge structure is seen, and where it isn't visible, all tell us how the material was organized as it emplaced.

An internal geological process could not be expected to generate structures with all these characteristics. A lack of discontinuites, fissures, or ridge like structures in the deep landslide basin aligned with the equator is also telling us much about the origin of this amazing ridge structure.