September 24, 2010
Looking like half of a figure eight, two of Saturn's moons appear conjoined in this Cassini spacecraft image.
The moon Dione, at the top in the image, is actually closer to the spacecraft here. However, because of the similar albedo, or reflectivity, of the two moons and because of the location of a particularly large crater near the south polar region of Dione, the moon appears to blend seamlessly with Rhea. The large, faint crater Evander is centered at about 57 degrees south latitude, 145 degrees west longitude and can also be seen in the Dione south polar map (see Dione Polar Maps - February 2010).
Lit terrain seen here is on the anti-Saturn side of Dione (1,123 kilometers, or 698 miles across) and on the area between the anti-Saturn and leading hemisphere on Rhea (1,528 kilometers, or 949 miles across).
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 27, 2010. The view was acquired at a distance of approximately 1.1 million kilometers (684,000 miles) from Dione and at a Sun-Dione-spacecraft, or phase, angle of 78 degrees. The view was acquired at a distance of approximately 1.6 million kilometers (994,000 miles) from Rhea and at a Sun-Rhea-spacecraft, or phase, angle of 78 degrees. Image scale is 7 kilometers (4 miles) per pixel on Dione and 10 kilometers (6 miles) on Rhea.
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