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Cassini captures this dual portrait of an apparently dead moon and one that is very much alive. Tethys (1,062 kilometers, 660 miles across), in the foreground, shows no signs of recent geologic activity. Enceladus (504 kilometers, 313 miles across), however, is covered in fractures and faults - near its south pole in particular - and spews icy particles into space from active vents.
Tethys' giant crater Odysseus lurks in the dark just west of the terminator. North on the moons is up.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Nov. 29, 2005 at a distance of approximately 970,000 kilometers (600,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 122 degrees. Cassini was then 1.1 million kilometers (700,000 miles) from Enceladus. Image scale is 6 kilometers (4 miles) per pixel on Tethys (at left) and 7 kilometers (4 miles) per pixel on Enceladus (at right).
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 Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. 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.