Saturn is remarkable in a number of ways; among all the planets we know of, it’s the least dense, and also the only one with a spectacularly visible set of rings. Composed of icy, dust-like material, these rings are not solid at all, but made up of particles that pass each other, stick together briefly and then fly apart once again.

Snowballs and planetesimals coalesce, only to be torn apart by tidal forces exerted by Saturn and its passing moons. Gaps in the inner rings are caused by the gravitational presence of moons themselves, while many of the outer rings — like Saturn’s E-ring, below — are actually caused by the moons themselves.