This page shows the results of high resolution simulations of Saturn's A ring with embedded moonlets. The point of these simulations is to try to figure out what Cassini is seeing in observations that appears as bright regions in both lit and dark side images of the rings. Our earlier work showed that adding in self-gravity and particle size distributions makes it harder for the standard propeller structures to form. This work is doing higher resolution simulations and also looking at radiative transfer modeling of the system to see how the simulated systems would look in different conditions.
Here is an example of this. This first image shows a rendering of the section of the simulation near the moonlet where each particle has been drawn as a dot of the proper size. You can see the gravity wakes as well as both a gap formed by the moonlet and some slight density enhancements that are called moonlet wakes. Note that the moonlet is drawn lighter colored and there is a transparent red circle drawn that is the size of the original moonlet. This allows us to see how much of the background material has built up on the moonet.
This isn't exactly what would be seen by a spacecraft like Cassini though. It is more like an ideal image of the system. In reality, light comes in and gets scattered around and some of it makes it to the camera. The figure below uses a first order RT model. This model does not include light scattering, only shadowing. The camera here is on the unlit side of the rings. Note that there are bright regions to the left and the right, but both are below (radially interior to) the moonlet and their radial separation is smaller than the separation between the moonlet wakes.
This has interesting implications for interpretation of Cassini images because radial separation is the primary measurement used to infer moonlet size. What is also interesting to note is that this viewing geometry was picked with care. Many viewing geometries showed nothing at all. Others, particularly on the lit side, showed the gaps very clearly. This one happened to do the best job of matching what is seen in observations. The intention of this work is to do sampling from many viewing geometries using a better RT model and also do it on many simulations. This particular simulation has a large moonlet, 130m in diameter. Many of the observations have features that lead us to infer a smaller size so a variety of moonlet sizes will also be used and compared.