MEDIA RELATIONS OFFICE <br />JET PROPULSION LABORATORY <br />CALIFORNIA INSTITUTE OF TECHNOLOGY<br />NATIONAL AERONAUTICS AND SPACE ADMINISTRATION<br />PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011<br />http://www.jpl.nasa.gov<br /> <br />Carolina Martinez (818) 354-9382<br />Jet Propulsion Laboratory, Pasadena, Calif. <br /> <br />Heidi Finn (720) 974-5859<br />Cassini Imaging Central Laboratory for Operations<br />Space Science Institute, Boulder, Colo.<br /> <br />News Release: 2004-149 June 14, 2004<br /> <br />Phoebe's Surface Reveals Clues to its Origin<br /> <br />Images collected during Cassini's close flyby of Saturn's moon,<br />Phoebe, have yielded strong evidence that the tiny object may contain<br />ice-rich material, overlain with a thin layer of darker material<br />perhaps 300 to 500 meters (980 to 1,600 feet) thick. <br /> <br />The surface of Phoebe is also heavily potholed with large and small<br />craters. Images reveal<br />bright streaks in the ramparts of the largest craters, bright rays<br />which emanate from smaller craters, and uninterrupted grooves across<br />the face of the body.<br /> <br />"The imaging team is in hot debate at the moment on the<br />interpretations of our findings," said Dr. Carolyn Porco, Cassini<br />imaging team leader at the Space Science Institute in Boulder, Colo. <br />"Based on our images, some of us are leaning towards the view that has<br />been promoted recently, that Phoebe is probably ice-rich and may be an<br />object originating in the outer solar system, more related to comets<br />and Kuiper Belt objects than to asteroids."<br /> <br />In ascertaining Phoebe's origin, imaging scientists are noting<br />important differences between the surface of Phoebe and that of rocky<br />asteroids which have been seen at comparable resolution. "Asteroids<br />seen up close, like Ida, Mathilde, and Eros, and the small martian<br />satellites do not have the bright 'speckling' associated with the<br />small craters that are seen on Phoebe," said Dr. Peter Thomas, an<br />imaging team member from Cornell University, Ithaca, N.Y.<br /> <br />The landforms observed in the highest resolution images also contain<br />clues to the internal structure of Phoebe. Dr. Alfred McEwen, an<br />imaging team member from the University of Arizona, Tucson, said,<br />"Phoebe is a world of dramatic landforms, with craters everywhere,<br />landslides, and linear structures such as grooves, ridges, and chains<br />of pits. These are clues to the internal properties of Phoebe, which<br />we'll be looking at very closely in order to understand Phoebe's<br />"I think these images are showing us an ancient remnant of the bodies<br />that formed over four billion years ago in the outer reaches of the<br />solar system," said Dr. Torrence Johnson, an imaging team member from<br />NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Battered and<br />beat-up as it is, it is still giving us clues to its origin and<br />history."<br /> <br />Phoebe may be an icy interloper from the distant outer solar system<br />which found itself captured by giant Saturn in its earliest, formative<br />years. Final conclusions on Phoebe's origins await a combination of<br />the results on Phoebe's surface structures, mass and composition<br />gathered from all 11 instruments, which collected data during the<br />flyby on June 11, 2004.<br /> <br />"This has been an impressive whirlwind flyby and it's only a curtain<br />raiser on the events about to begin," said Porco.<br /> <br />Cassini arrives in orbit around Saturn on the evening of June 30, 2004<br />(July 1 Universal Time).<br />The Cassini-Huygens mission is a cooperative project of NASA, the<br />European Space Agency and the Italian Space Agency. JPL, a division of<br />the California Institute of Technology in Pasadena, manages the<br />Cassini-Huygens mission for NASA's Office of Space Science,<br />Washington, D.C. The Cassini orbiter and its two onboard cameras were<br />designed, developed and assembled at JPL. The imaging team is based<br />at the Space Science Institute, Boulder, Colo.<br /> <br />For the latest images and information about the Cassini-Huygens<br />mission, visit <br /> <br />http://saturn.jpl.nasa.gov <br /> <br />and the Cassini imaging team home page, <br /> <br />http://ciclops.org . <br /> <br />For more information on NASA programs, visit <br /> <br />http://www.nasa.gov .