Cassini's Doubleheader Flybys Score Home Run

New images, mosaics and a movie of these bodies are available at http://saturn.jpl.nasa.gov , http://www.nasa.gov/cassini and http://ciclops.org .

Images of Tethys taken during Cassini's close approach to the moonon Sept. 24, 2005, reveal an icy land of steep cliffs and craters.Cassini photographed the moon's south pole, a region not seen by NASA'sVoyager spacecraft.

A giant rift called Ithaca Chasma cuts across the disk of Tethys.Much of the topography in this region, including that of Ithaca Chasma,has been thoroughly hammered by impacts. This appearance suggests thatthe event that created Ithaca Chasma happened very long ago.

Near a prominent peaked crater named Telemachus are the remnants ofa very old crater named Teiresias. The ancient impact site is badlyoverprinted and eroded by impact weathering and degradation. All thatremains is a circular pattern of hummocks that mark where the oldcrater rim existed. Many of the fresh-appearing craters exhibitunusually bright crater floors, in contrast to the dark-floored cratersseen on Saturn's oddly tumbling moon Hyperion.

Images of Hyperion taken on Sept. 26 show a surface dotted withcraters and modified by some process, not yet understood, to create astrange, "spongy" appearance, unlike the surface of any other Saturnmoon.

A false-color image of Hyperion reveals crisp details and variationsin color across the strange surface that might represent differences inthe composition of materials. Hyperion has a notably reddish tint whenviewed in natural color.

Scientists are extremely curious to learn what the dark material isthat fills many craters on this moon. Features within the dark terrain,including a 200-meter-wide (650-feet) impact crater surrounded by raysand numerous bright-rimmed craters, indicate that the dark material maybe only tens of meters thick with brighter material beneath.

Scientists will also be examining Cassini's sharp views in hopes ofdetermining whether there have been multiple episodes of landslides onHyperion. Such "downslope" movement is evident in the filling ofcraters with debris and the near elimination of many craters along thesteeper slopes. Answers to these questions may help solve the mysteryof why this object has evolved different surface forms from other moonsof Saturn.

Cassini flew by Hyperion at a distance of only 500 kilometers (310miles). Hyperion is 266 kilometers (165 miles) across, has an irregularshape, and spins in a chaotic rotation. Much of its interior is emptyspace, explaining why scientists call Hyperion a rubble-pile moon. Thisflyby was Cassini's only close encounter with Hyperion in the primemission four-year tour. Over the next few months, scientists will studythe data in more detail.

Cassini flew by Tethys at a distance of approximately 1,500kilometers (930 miles) above the surface. Tethys is 1,071 kilometers(665 miles) across and will be visited again by Cassini in the summerof 2007.

The Cassini-Huygens mission is a cooperative project of NASA, theEuropean Space Agency and the Italian Space Agency. The Jet PropulsionLaboratory, a division of the California Institute of Technology inPasadena, manages the Cassini-Huygens mission for NASA's ScienceMission Directorate, Washington, D.C. The Cassini orbiter and its twoonboard cameras were designed, developed and assembled at JPL. Theimaging team is based at the Space Science Institute, Boulder, Colo.