Saturn's moon Dione passes by the moon Tethys in this Cassini depiction of a "mutual event" in which one moon passes close to or in front of another.
Mutual event observations help scientists refine their understanding of the orbits of Saturn's moons. See PIA11692 to watch a movie of a mutual event. Lit terrain seen here is on Saturn-facing side of Tethys (1062 kilometers, 660 miles across) and on the trailing hemisphere of Dione (1123 kilometers, 698 miles across).
The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 26, 2010. The view was obtained at a distance of approximately 2 million kilometers (1.2 million miles) from Dione and 2.4 million kilometers (1.5 million miles) from Tethys. Image scale in the original image was 12 kilometers (7 miles) per pixel on Dione and 14 kilometers (9 miles) per pixel on Tethys. The image was contrast enhanced and magnified by a factor of two to enhance the visibility of surface features.
The Cassini Equinox Mission is a joint United States and European endeavor. 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 was designed, developed and assembled at JPL. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.