open access

https://hdl.handle.net/2115/34714

Planetary Rings : Particle Properties and Evolution

日本語

2008-03-31

北海道大学低温科学研究所

Low Temperature Science

66

73-81

2章 惑星形成と氷微粒子

All the four giant planets in our Solar System have rings, thus ring-satellite systems seem to be a natural byproduct of giant planet formation process. Therefore, studies on the origin and evolution of ring-satellite systems would constrain the formation processes of giant planets. Saturn's rings are mainly composed of water ice, and particles in the main rings have sizes between centimeters to several meters. We first describe effects of normal and tangential coefficients of restitution of icy ring particles on dynamical evolution of planetary rings. Restitution coefficients for icy particles for low-velocity impacts relevant to Saturn's rings have been measured by laboratory impact experiments. Restitution coefficients influence random velocity evolution of ring particles, their rotational states, and accretional evolution. We will also discuss possible effects of adhesive forces between ring particles on accretional evolution and structure formation in rings, although it is not clear at present whether nongravitational cohesive forces would play a major role in the dynamics of planetary rings. Finally, we will discuss effects of meteoroid impacts on the creation and evolution of planetary rings. Dilute dust rings including the Jovian rings are created by meteoroid impacts on small satellites. Such impacts would also cause compositional evolution of Saturn's rings. Further theoretical as well as observational studies of compositional evolution of Saturn's rings would provide a unique constraint on the origin and evolution of the rings.

紀要論文

Version of Record

1880-7593