Saturn`s moon spawning moonlets discovered

Astronomers have discovered Saturn`s biggest moon creating a trail of giant snowballs.

Last Updated: Jul 23, 2010, 17:03 PM IST

Washington: For the first time, astronomers
have discovered Saturn`s biggest moon creating a trail of
giant snowballs as big as 12 miles in diameter when it enters
the innermost edge of the planet`s ring.

The scientists found that the moon, Prometheus, which
passes through the innermost edge of the ring in about every
68 days, lifts out ring particles which then begin to clump
and take on a life of their own over time.

According to the scientists, the larger and closer
satellite of Saturn cruises a bit faster than the particles in
the ring and is slightly inclined relative to the ring`s
plane.

It collides with the diffuse, inner edge of the F-ring
(the outermost ring of the planet) where the moon`s gravity
is strong enough to pull streamers of particles from the ring,
creating channels.

Over time, the disrupted particles -- mostly dense,
sticky ice -- can take on a life of their own, clumping
together under their own growing gravitational force, said the
scientists who discovered the phenomenon by analysing images
by NASA`s Saturn-orbiting Cassini spacecraft.

"We`ve never actually seen this before. You can see a
real cause and effect. These objects didn`t exist before
Prometheus passed," lead researcher Carl Murray, with Queen
Mary, University of London, told Discovery News.

Future visits by Prometheus could stoke a snowball`s
growth -- or it could destroy it, they said.

"Once Prometheus passes by, it gives these objects a
kick. They have about 68 days to sort of get things together
before Prometheus comes around again," Murray said.

"Whether at the end of the day you end up with a fully
formed satellite we don`t know. That`s something we want to
look at. Maybe these objects are precursors of fully formed
satellites," he said.

The complicated physics in Saturn`s ring -- particularly
the F-ring where the planet`s tidal forces wane and objects
can begin to form under their own gravitational sway -- serve
as a living laboratory for understanding how planets form,
said Cassini project scientist Linda Spilker, with NASA`s Jet
Propulsion Laboratory in California.

"You can think of Saturn`s rings as miniature versions of
the disks where planets form. The same physical processes are
occurring," Spiker said.

The findings are published online in the Astrophysical
Journal Letters.

PTI