|
|
The images taken by the NASA/ European Space Agency (ESA) spacecraft on the 11 June 2004 show the surface of Phoebe to also be heavily potholed with large and small craters. Images reveal bright streaks in the walls of the largest craters, bright rays emanate from smaller craters, and uninterrupted grooves across the face of the moon.
Image: NASA.
"The imaging team is in hot debate at the moment on the interpretations of our findings," said Dr. Carolyn Porco, Cassini imaging team leader at the Space Science Institute in Boulder, USA. "Based on our images, some of us are leaning towards the view that has been promoted recently, that Phoebe is probably ice-rich and may be an object originating in the outer solar system, more related to comets and Kuiper Belt objects than to asteroids."
In ascertaining Phoebe's origin, imaging scientists are noting important differences between the surface of Phoebe and that of rocky asteroids which have been seen at comparable resolution. "Asteroids seen up close, like Ida, Mathilde, and Eros, and the small Martian satellites do not have the bright 'speckling' associated with the small craters that are seen on Phoebe," said Dr. Peter Thomas, an imaging team member from Cornell University, Ithaca, USA.
Phoebe may be an icy body from the distant outer Solar System which found itself captured by Saturn in its earliest, formative years. Final conclusions on Phoebe's origins await a combination of the results on Phoebe's surface structures, mass and composition gathered from all eleven instruments which were trained on the moon during the flyby.
"This has been an impressive whirlwind flyby and it's only a curtain raiser on the events about to begin," said Porco. Cassini arrives in orbit around Saturn on the morning of 1 July 2004. From there, it will conduct 76 orbits of Saturn over four years and execute 52 close encounters with seven other Saturnian moons. Of these, 45 will be with the largest and most interesting one, Titan. On 25 December, Cassini will release the Huygens probe, which will descend through Titan's thick atmosphere to investigate its composition and complex organic chemistry.
More info: Cassini-Huygens at ESA
|
