Explanation:
How old are Saturn's rings?
No one is quite sure.
One possibility is that the rings formed relatively recently in our
Solar System's history, perhaps only about 100 million years ago when
a moon-sized object
broke up near Saturn.
Evidence for a young ring age includes a basic
stability
analysis for rings,
and the fact that the rings are so bright and
relatively unaffected by numerous small dark
meteor impacts.
New
evidence, however, raises the possibility that some of
Saturn's rings
may be billions of years old and so almost as
old as Saturn itself.
Inspection of images by the Saturn-orbiting Cassini spacecraft
indicates that some of
Saturn's ring particles temporarily
bunch and collide, effectively recycling
ring particles by bringing
fresh bright ices to the surface.
Seen here,
Saturn's rings were imaged in their true colors by the
robotic
Cassini in late October.
Icy bright Tethys,
a moon of Saturn likely brightened by a sandblasting
rain of ice from sister moon
Enceladus, is visible in front of
the darker rings.
APOD presents: Astronomy Pictures of the Year for 2007
