Cassini Captures Prometheus Red-Handed

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

Heidi Finn (720) 974-5859
Cassini Imaging Central Laboratory for Operations
Space Science Institute, Boulder, Colo.

Image Advisory: 2004-282 December 3, 2004

Cassini Captures Saturn Moon Red-Handed

Stealing is a crime on Earth, but at Saturn, apparently it
is routine. The Cassini spacecraft has witnessed Saturn's
moon Prometheus snatching particles from one of Saturn's
rings.

This potato-shaped moon is also believed to be responsible
for kinks within Saturn's thin F ring, a contorted, narrow
ring flanked by two small moons, Prometheus and Pandora.
The thievery and the detailed behavior of kinks were
observed for the first time ever in images taken by the
Cassini spacecraft.

In an image taken on Oct. 29, Prometheus is seen stealing
particles from the F ring while connected to the ringlets by
a faint streak of material. A movie sequence of the ring,
taken on Oct. 28, captures in freeze-frame motion the
zigzagging kinks and knots, some of which are almost
certainly caused by Prometheus.

The new still and movie are available at
http://saturn.jpl.nasa.gov , http://www.nasa.gov/cassini and
http://ciclops.org .

The kinks look like "hiccups" traveling around the ring.
Consisting of 44 frames taken three minutes apart, the
sequence represents almost two hours, or about one-eighth of
the orbital period of F ring particles around the planet.

Cassini was on a flight path that took the spacecraft away
from the planet and farther south, so that the rings appear
to tilt upward. The top portion of the F ring is closer to
the spacecraft, while the bottom portion is farther away and
curves around the far side of Saturn.

Scientists are not sure exactly how Prometheus is
interacting with the F ring here, but they have speculated
that the moon might be gravitationally pulling material away
from the ring. Scientists speculate that the ring particles
may end up in a slightly different orbit from the one they
were in prior to getting a 'kick' from the moon. These kicks
occur at specific locations in the rings and can actually
cause large waves or knots to form. In the still image,
gaps in the diffuse inner strands are seen. All these
features appear to be due to the influence of Prometheus in
ways that are not fully understood.

Saturn's moon Prometheus is following in the footsteps of
the legendary Titan for which it is named. In Greek
mythology, Prometheus stole fire from the gods and gave it
to the mortals.

Scientists will use what they learn about Prometheus'
interaction with the F ring to understand the gravitational
exchanges between moons and rings, which give rise to so
much of the structure that is observed in Saturn's rings.

The Cassini-Huygens mission is a cooperative project of
NASA, the European Space Agency and the Italian Space
Agency. The Jet Propulsion Laboratory, a division of the
California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission
Directorate, Washington, D.C. The Cassini orbiter and its
two onboard cameras were designed, developed and assembled
at JPL. The imaging team is based at the Space Science
Institute, Boulder, Colo.

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