World Reacts to Ringworld's Camera
|Rings imaged June 30, 2004 as Cassini passed over the thin layer of dust and rock. Bands are created by resonance conditions between Saturn and its moons, which tend to clear out regions of lower relative densities. Image Credit: JPL/NASA
After becoming the first spacecraft to enter Saturn's orbit, Cassini sent back this image of a portion of the planet's rings. It was taken by the spacecraft's narrow angle camera and shows the dark, or unlit, side of the rings.
Following the spacecraft's successful orbital insertion, mission scientists hope to receive approximately sixty images from what they refer to as the 'unique science' portion of the Cassini tour. This phase represents the closest approach to Saturn and includes flying approximately 12,000 miles above the cloud tops.
Looking down from Cassini's camera, the view shows also the elaborate ring structure that is banded in primary regions lettered by historical convention between 'A' and 'G'. The ring letters correspond to their order of discovery. Scientists hope to find even more wispy bands extending out with finer structure now that they have assets in place for the full four-year tour.
The rings extend across a vast plane but in places may be only 60 feet thick when viewed edgewise. Cassini flew through a region considered low in dust density between the F and G rings.
Scientists hope to resolve a long-standing mystery dating back to the first Voyager flyby of Saturn more than two decades ago. While amateur telescopes can resolve the B ring, or thickest band, even space telescopes have not been able to study a phenomenon that has come to be called 'ring spokes'. The formation and destruction of these outwardly radiating density changes seem to defy the expected rotational symmetry that form the rings in the first place. When viewed in time lapse movies, the spokes rotate around the planet in a highly dynamic way that suggests finer structure than even the filigree of the radial bands.
Among the main mission goals, the tour features a study of Saturn's 31 moons. Saturn is also unlike other planets in its magnetic fields which rotate with the main rotation thus regenerating a new dynamo each Saturnian day. The typical torus expected from magnetic poles has surprised scientists who want to understand how this torus changes with solar wind, seasons, and even auroral showers near the poles.
|Mysterious ring spokes first seen by Voyager. Image Credit: JPL/NASA
The weather report on Saturn is unlike any terrestrial equivalent, as a typical day on the ringed world features atmospheric hurricanes the size of Earth and liquid helium rain. The average temperature varies depending on height in the gas giant but plunges to a frigid minus 227 degrees Fahrenheit typically. Air pressure at the top of the atmosphere rivals the best vacuum achievable in a laboratory but increases to crushing densities just below the cloud tops.
After today's transmission of the unique science images follows a planned Saturday orbital correction which should place the orbiter into a large ellipse that will encircle Saturn once every four months. The primary Cassini mission calls for a four-year tour but mission planners expect onboard resources to last years beyond for what is hoped will become a lengthy extended mission.
|Rings imaged June 30, 2004 as Cassini flew over the Saturnian dust and rock layer. Some particles are dust motes while rocks in the thick B band can range to the size of a house.Image Credit: JPL/NASA
The Cassini-Huygens mission includes 17 countries and international representatives from the science community expressed their hope for the next four years in an ESA release. 'I've waited 15 years for this moment,' said Dr Andrew Coates of the UK's Mullard Space Science Laboratory and Co-Investigator on the Cassini spacecraft's Plasma Electron Spectrometer,' and now our 4-year tour of discovery can really begin'.
Speaking from NASA's Jet Propulsion Laboratory in Pasadena California, Dr. Michele Dougherty of Imperial College London and Principal Investigator for the magnetometer instrument on Cassini, said,' the spacecraft performed superbly tonight and critical data was taken during the 95 minute engine burn period.'
Prof. Carl Murray from Queen Mary, University of London, involved on the Cassini cameras, was equally ecstatic,' this is a remarkable achievement and a wonderful example of a successful, international collaboration. The arrival of the Cassini-Huygens spacecraft at Saturn heralds a new age in our understanding of this majestic planet and its retinue of moons and rings. I have no doubt that the wealth of data to be returned will also provide unique insights into the origin and evolution of planetary systems. The next four years will be tremendously exciting for everybody.'
A jubilant and relieved Prof. John Zarnecki of the UK's Open University added, 'For me it's been 7 years in the planning, 7 years of travel and 95 minutes of purgatory - but now we've made it and the next stop is Titan'. For Prof. Zarnecki, Principal and Co-Investigator on two key instruments onboard the Huygens probe currently piggy backing the Cassini mothership, there are still more nail-biting moments ahead. Huygens will separate from Cassini on the 25 December this year and parachute down through the nitrogen-rich atmosphere of Titan, Saturn's largest moon, to land on the surface on the 14 January 2005.
The Saturn Orbit Insertion was the last and most critical maneuver for the Cassini orbiter and the spacecraft, which is in perfect shape, will now commence science operations during its 76 orbits of the ringed planet.
Related Web Pages
Saturn Edition, Astrobiology Magaz.
Cassini Closes In on Saturn
Saturn-- JPL Cassini Main Page
Lord of the Rings
Space Science Institute, Imaging Team Boulder, Colorado
Saturn: The Closest Pass