The moon Rhea moves behind Saturn's largest moon, Titan, in this "mutual event" imaged by the Cassini spacecraft.
Mutual event sequences, in which one moon passes close to or in front of another, help scientists refine their understanding of the orbits of Saturn's moons. Part of Rhea's southern hemisphere is also visible here through the haze of Titan's atmosphere. See Catching Big Sister to watch a movie of a mutual event.
Titan has been brightened by a factor of 1.5 relative to Rhea. This view looks toward the anti-Saturn side of Titan (5,150 kilometers, or 3,200 miles across) and the trailing hemisphere of Rhea (1,528 kilometers, or 949 miles across).
The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on Nov. 27, 2009. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Titan and from 2.3 million kilometers (1.4 million miles) from Rhea. Image scale in the original image was 14 kilometers (9 miles) per pixel on Titan and 27 kilometers (17 miles) per pixel on Rhea. The image has been magnified by a factor of two and contrast-enhanced to aid visibility.
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.
Credit: NASA/JPL/Space Science Institute