Waves and Small Particles in Ring A
Three simultaneous radio signals at wavelengths of 0.94, 3.6, and 13 centimetres (Ka-, X-, and S-bands) were sent from Cassini through the rings to Earth. The observed change of each signal as Cassini moved behind the rings provided a profile of the distribution of ring material and an optical depth profile.
This simulated image was constructed from the measured optical depth profiles of the Cassini Division and ring A. It depicts the observed structure at about 10 kilometres in resolution. The image shows the same ring A region depicted in a similar image, using a different colour scheme to enhance the view of a remarkable array of over 40 wavy features called "density waves" uncovered in the 3 May radio occultation throughout ring A.
Colour is used to represent information about ring particle sizes based on the measured effects of the three radio signals. Shades of red indicate regions where there is a lack of particles less than 5 centimetres in diameter. Green and blue shades indicate regions where there are particles of sizes smaller than 5 centimetres and 1 centimetre, respectively.
Note the gradual increase in shades of green towards the outer edge of ring A. It indicates gradual increase in the abundance of 5-centimeter and smaller particles. Note also the blue shades in the vicinity of the Keeler gap (the narrow dark band near the edge of ring A). They indicate increased abundance of even smaller particles of diameter less than a centimetre. Frequent collisions between large ring particles in this dynamically active region likely fragment the larger particles into more numerous smaller ones.