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Cassini flies past Tethys, revealing spectacular details CASSINI PHOTO RELEASE Posted: October 1, 2005
The giant rift Ithaca Chasma cuts across the disk. Much of the topography seen here, including that of Ithaca Chasma, has a soft, muted appearance. It is clearly very old and has been heavily bombarded by impacts over time. Many of the fresh-appearing craters (ones with crisp relief) exhibit unusually bright crater floors. The origin of the apparent brightness (or "albedo") contrast is not known. It is possible that impacts punched through to a brighter layer underneath, or perhaps it is brighter because of different grain sizes or textures of the crater floor material in comparison to material along the crater walls and surrounding surface. The moon's high southern latitudes, seen here at the bottom, were not imaged by NASA's Voyager spacecraft during their flybys of Tethys 25 years ago. The mosaic is composed of nine images taken during Cassini's close flyby of Tethys (1,071 kilometers, or 665 miles across) on Sept. 24, 2005, during which the spacecraft passed approximately 1,500 kilometers (930 miles) above the moon's surface. This view is centered on terrain at approximately 1.2 degrees south latitude and 342 degrees west longitude on Tethys. It has been rotated so that north is up. The clear filter images in this mosaic were taken with the Cassini spacecraft narrow-angle camera at distances ranging from 71,600 kilometers (44,500 miles) to 62,400 kilometers (38,800 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees. The image scale is 370 meters (1,200 feet) per pixel.
This false-color image, created with infrared, green and ultraviolet frames, reveals a wide variety of surface colors across this terrain. The presence of this variety at such small scales may indicate a mixture of different surface materials. Tethys was previously known to have color differences on its surface, especially on its trailing side, but this kind of color diversity is new to imaging scientists. This view is centered on terrain at approximately 4.2 degrees south latitude and 357 degrees west longitude on Tethys. The view has been rotated so that north on Tethys is up. The images for this view were obtained using the Cassini spacecraft narrow-angle camera at distances ranging from approximately 18,400 to 19,000 kilometers (11,400 to 11,800 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 17 degrees. Image scale is 213 meters (700 feet) per pixel.
Above the prominent peaked crater Telemachus are the remnants of a very old crater (at the 10 o'clock position relative to Telemachus) named Teiresias. The ancient impact site is so badly overprinted and eroded by impact weathering and degradation that all that remains is a circular pattern of hummocks that mark where the old crater rim existed. This view is centered on terrain at approximately 1.2 degrees south latitude and 342 degrees west longitude on Tethys. The view is rotated so that north is about 40 degrees to the right. This clear filter view was taken during Cassini's close approach to Tethys on Sept. 24, 2005. The image was acquired using the Cassini spacecraft narrow-angle camera at a distance of approximately 69,200 kilometers (43,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 21 degrees. Image scale is 410 meters (1,350 feet) per pixel.
The ridges around Ithaca Chasma have been thoroughly hammered by impacts. This appearance suggests that Ithaca Chasma as a whole is very old. There is brighter material in the floors of many craters on Tethys. That's the opposite situation from Saturn's oddly tumbling moon Hyperion, where dark material is concentrated in the bottoms of many craters. This view is centered on terrain at approximately 2.5 degrees south latitude and 352 degrees west longitude on Tethys. North on Tethys is toward the right in this view. This clear filter view was obtained using the Cassini spacecraft narrow-angle camera at a distance of approximately 32,300 kilometers (20,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 20 degrees. Image scale is 190 meters (620 feet) 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. |
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