Ring structure among the other giant planets is not as
diverse as Saturn’s. Most rings other than Saturn’s are quite
narrow, although a few are diffuse. Diffuse rings tend to be
sparsely populated and have characteristics quite different
from Saturn’s tightly packed bright rings. The separations
between particles in diffuse rings are generally very large,
and the occasional collisions between particles can cause
their individual orbits to become eccentric, inclined, or
both. Because it is unlikely
that these disturbed orbits
will experience a restoring
collision, the particles tend to
remain in their noncircular,
non-coplanar orbits. For this reason, diffuse rings spread
out horizontally and thicken vertically, sometimes without
any obvious boundaries. These characteristics make diffuse
rings diffi cult to detect at most viewing angles. When seen
under backlit conditions however, diffuse rings appear to
light up because of the strong forward scattering of very
small ring particles by sunlight (see Excursions 8.2 and