Moons that Share
September 19, 2007
The two moons pictured here each share their orbits with other bodies.
Dione (1,126 kilometers, or 700 miles across, at left) has two much smaller "Trojan" moons, Helene and Polydeuces (not seen here), that orbit 60 degrees in front of and behind it in its orbit. Epimetheus (116 kilometers, or 72 miles across, at right) shares its orbital path with Janus, and the two moons swap positions every few years -- one moving just a bit closer to Saturn and the other moving slightly farther away.
This view looks toward the unilluminated side of the rings from less than a degree above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 28, 2007. Cassini was approximately 2.9 million kilometers (1.8 million miles) from Saturn when it acquired this view. Image scale is 15 kilometers (9 miles) per pixel on Dione.
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 .
Credit: NASA/JPL/Space Science Institute