Cassini images reveal the existence of a faint arc of material orbiting
with Saturn's small moon Anthe.
The moon is moving in a counterclockwise direction in this perspective,
and is about to reach the ansa—the point of maximum elongation—as
seen by the viewer, in its curving path around Saturn.
In this image, most of the visible material in the arc lies ahead of Anthe
(2 kilometers, or 1 mile across) in its orbit. However, over time the moon
drifts slowly back and forth with respect to the arc. Also ahead of the
moon is a dark channel where the arc appears split into two strands, and
these then merge farther around the orbital path. The arc extends over
about 20 degrees in longitude (about 5.5 percent of Anthe's orbit) and
appears to be associated with a gravitational resonance caused by Mimas.
Micrometeoroid impacts on Anthe are the likely source of the arc material.
The orbit of Anthe lies between the larger moons Mimas and Enceladus.
Anthe shares this region with two other small moons, Pallene (4 kilometers,
or 3 miles across) and Methone (3 kilometers, or 2 miles across). Methone
also possesses an arc (see PIA11102), while Pallene is known to
orbit within a faint, complete ring of its own (see PIA08328).
Cassini imaging scientists believe the process that maintains the Anthe
and Methone arcs is similar to that which maintains the arc in the G ring
(see PIA08327). This view looks toward the un-illuminated side of the
rings from about 3 degrees above the ringplane. The view has been rotated
so that Saturn's north pole would point upward. The general brightness of
the image (along with the faint horizontal and vertical banding pattern)
results from the long exposure time of 32 seconds required to capture the
extremely faint ring arc and the processing needed to enhance its
visibility (which also enhances the digital background noise in the
image). The image was digitally processed to remove most of the background
noise. The long exposure also produced star trails in the background.
The image was taken in visible light with the Cassini spacecraft narrow-angle
camera on April 4, 2008. The view was acquired at a distance of
approximately 1.2 million kilometers (746,000 miles) from Anthe and at a
sun-Anthe-spacecraft, or phase, angle of 23 degrees. Image scale is 7
kilometers (4 miles) per pixel.
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 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 operations center is based at the Space
Science Institute in Boulder, Colo.
For more information about the Cassini-Huygens mission visit
http://saturn.jpl.nasa.gov/. The Cassini imaging team
homepage is at http://ciclops.org.
