Hidden Janus

The small moon Janus is almost hidden between the planet's rings and the larger moon Rhea.
PIA NumberPIA12558
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The small moon Janus is almost hidden between the planet's rings and the larger moon Rhea.

The northern part of Janus can be seen peeking above the rings in this image of a "mutual event" in which Janus (179 kilometers, or 111 miles across) moved past Rhea (1,528 kilometers, or 949 miles across). Mutual event observations such as this one, in which one moon passes close to or in front of another, help scientists refine their understanding of the orbits of Saturn's moons. See Catching Big Sister to watch a movie of a mutual event.

The view was acquired at a distance of approximately 2.7 million kilometers (1.7 million miles) from Janus and about 3.1 million kilometers (1.9 million miles) from Rhea. Rhea is a slightly overexposed in this image.

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 11, 2009. Scale on Janus is about 16 kilometers (10 miles) per pixel. Scale on Rhea is about 19 kilometers (12 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 .

Credit: NASA/JPL/Space Science Institute