  The true reason for partition of the Saturn ring as well as rings of other
planets into great many of sub-rings is found. This reason is the theorem of
Zelikin-Lokutsievskiy-Hildebrand about fractal structure of solutions to
generic piece-wise smooth Hamiltonian systems. The instability of
two-dimensional model of rings with continues surface density of particles
distribution is proved both for Newtonian and for Boltzmann equations. We do
not claim that we have solved the problem of stability of Saturn ring. We
rather put questions and suggest some ideas and means for researches.
