Cassini offers this lovely comparison between two of Saturn's satellites,
Dione and Tethys, which are similar in size but have very different
surfaces.
Extensive systems of bright fractures carve the surface of Dione (1,118
kilometers, or 695 miles across). The double-pronged feature Carthage
Linea points toward the crater Turnus at the nine o'clock position near
the terminator, and Palatine Linea runs toward the moon's bottom limb near
the five o'clock position.
In contrast, the surface of Tethys (1,071 kilometers, or 665 miles across)
appears brighter and more heavily cratered. The large crater Penelope is
near the eastern limb. The huge rift zone Ithaca Chasma, which is 3 to 5
kilometers (2 to 3 miles) deep and extends for about 2,000 kilometers
(1,200 miles) from north to south across Tethys, is hidden in shadow just
beyond the terminator. For comparison, the Grand Canyon in Arizona is
about 1.5 kilometers (1 mile) deep, and about 450 kilometers (280 miles)
long.
The image was taken in visible light with the Cassini spacecraft
narrow-angle camera on March 7, 2005, at a distance of approximately 1.5
million kilometers (908,000 miles) from Tethys and 1.6 million kilometers
(994,000 miles) from Dione. The image scale is 9 kilometers (6 miles) per
pixel on Tethys, and 10 kilometers (6 miles) per pixel on Dione.
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 team is based at the Space Science
Institute, Boulder, Colo.
For more information about the Cassini-Huygens mission, visit
http://saturn.jpl.nasa.gov and the Cassini imaging team home page,
http://ciclops.org.
