Propeller Shadows on Saturns Rings
Explanation:
What created these unusually long shadows on Saturn's rings?
The dark shadows -- visible near the middle of the image -- extend opposite the Sun
and, given their length, stem from objects having heights up to a few kilometers.
The long shadows were unexpected given that the usual thickness of
Saturn's A and B rings is only about 10 meters.
After considering the choppy but elongated shapes apparent near the
B-ring edge, however,
a
leading theory
has emerged that some kilometer-sized moonlets exist there that have enough gravity
to create even larger vertical deflections of nearby small ring particles.
The resulting ring waves are called
propellers, named for
how they appear individually.
It is these coherent groups of smaller ring particles that are hypothesized to be
casting the long shadows.
The
featured image
was taken by the
robotic Cassini spacecraft currently orbiting Saturn.
The image was captured in 2009, near
Saturn's equinox, when sunlight streamed directly over
the
ring plane and caused the longest shadows to be cast.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.