Saturday, November 19, 2011

Cassini Saturn's Rings at a Glance.


Beautiful, glamorous and mysterious, Saturn's rings are among the most recognizable features in the solar system. They spread over hundreds of thousands of kilometers, yet they are extremely thin – perhaps only 10 meters (about 30 feet) thick. The rings consist of billions of individual particles of mostly water ice which create waves, wakes and other structures.

Named alphabetically in order of their discovery, the order of the main rings outward from Saturn is D, C, B, A, F, G and E. (SeeSaturn's Rings at a Glance.) There are also several other faint unnamed rings made up of very fine icy particles.

Scientists still aren't sure exactly how old the rings are. Whether they date back to the early history of the Solar System or formed as recently as the period when the first dinosaurs roamed the Earth is a matter under investigation by Cassini scientists.

Whenever they first formed, it is clear that the rings we observe today were not all created in exactly the same way. For instance, Cassini found that a great plume of icy material blasting from the moon Enceladus is a major source of material for the expansive E ring. Additionally, Cassini has found that most of the planet's small, inner moons appear to orbit within partial or complete rings formed from particles blasted off their surfaces by impacts of micrometeoroids. 

Rings Aglow: Saturn's softly glowing rings shine in scattered sunlight.
The spacecraft began returning valuable information about the rings even before it slipped into Saturn orbit in July 2004. During the Saturn orbital insertion maneuver, the spacecraft obtained invaluable data about ring structure, including stunningly high-resolution images.

"The images found evidence for new processes whereby particle sticking and self gravity interact to form structures never seen before," explains Dr. Jeff Cuzzi, a research scientist at NASA's Ames Research Center and Cassini's interdisciplinary scientist for rings and dust. "High-quality stellar occultations by Cassini’s Ultraviolet Imaging Spectrograph and its Visible and Infrared Mapping Spectrometer, in addition to the camera images, reveal hundreds of never-before-seen spiral density and bending waves, as well as the fine-scale structure of gravitational instabilities in the rings and how they vary with location. The properties of these 'gravity wakes' are also seen in thermal [infrared] emission from the rings."

Cassini has also discovered new ringlets, new moons near the rings, a moon stealing particles from the narrow F ring, features resembling straw and rope, and dark contaminant material in the rings similar to dark material on the moons Phoebe and Iapetus. The mission is poised to reveal ever more about the nature of Saturn's remarkable rings as the spacecraft continues its journey.

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