1. Some Peculiar Features In Saturn’s Rings Quentin Donnellan

2. “In the universe there are spheres and there are discs; given the correct mechanisms one can become the other” Carolyn Porco

4. Basics… Cassini radio image > 5 cm < 5 cm large 99.9% pure water ice 3x10 19 kg 5-30 m thick

5. Particle size Roche limit Particles over a certain size will be torn apart by tidal forces Accretion discs inside the Roche limit should not coalesce beyond a certain size

6. Dominant features *Titan

7. Dominant features *Mimas

8. Dominant Features Pan Daphnis

9. Moons carve out gaps/features Rings are Keplerian…

10. Some disturbances are quite elegant

11. Prometheus Pandora F-Ring Teamwork

12. Some are not big enough… Moonlets embedded in the rings create keplerian wakes

13. Propellers

14. Upon further inspection, it ain’t that simple…

15. Density Waves In the 1960’s astronomers theorized the origins of spiral arms in galaxies as artifacts of “density waves”

16. Density Waves “Traffic Jams” of material increase the local density of the galactic disc and increase the local rate of star formation

17. Well, the rings around Saturn are essentially just a “disc”…

18. Density Waves at Saturn Analogous to spiral arms of galaxies, just much more tightly wound, caused by resonance excitation by moons

19. Also bending… 2004, A ringDensity wave bending wave (Vertical undulations)

20. This is advanced dynamics

21. So we can explain all of the peculiarities in the rings by the tugging of moons… … right?

22. Viscosity B ring: very dense We would expect such a high viscosity to dampen any waves excited into this ring

23. Viscosity But the viscosity of the ring is such that the random motions of the particles in the ring actually amplify waves

24. The rings, much like guitar strings, have natural modes which can become self-excited and amplified due to “viscous overstability” http://www.youtube.com/watch?v=tA2eqTZijwI

25. The equinox reveals more clues

26. I know you’re there Janus

27. Back to Daphnis

28. Vertical Structures 1-3 km in height

29. Back to the B-Ring

30. Back to the propellers

31. Complicated system… So the rings are very complicated Waves induced by moons Paths cut out by moons Material dragged up and down by moons Waves induced by the rings themselves

32. Extensions Can we treat all disc structures similarly?