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Science & Space

Cassini gets ringside view of Saturn's mysteries

Orbiting spacecraft beams back best images of planet's rings

By Michael Coren

Saturn and its moon Titan

  • SATURN: Planet second in size to Jupiter with a diameter of 74,898 miles (120,511 km). Seven rings of ice and rock particles with 31 known moons. Visited by Pioneer 11 (1979), Voyager 1 (1980), Voyager 2 (1981).

  • TITAN: Largest Saturnian moon. May harbor organic compounds similar to those predating life on Earth. Temperature is minus 290 degrees Fahrenheit.

  • CASSINI ORBITER: Launched Oct. 15, 1997. Spacecraft is 22 feet long and weighs 12,593 pounds (5,667 kg). Runs on nuclear power. Will orbit Saturn 76 times over four years.

  • HUYGENS PROBE: Spacecraft is 8.9 feet in diameter and 705 pounds (317 kg). Will be released from Cassini on Dec. 24 and enter Titan's atmosphere on Jan. 14.

  • MISSION COST: $3.3 billion, shared by NASA, ESA, Italian Space Agency.
    Gallery: Saturn's rings

    Cassini crosses ring gaps and is pounded by dust bits (NASA)

    • Interactive: Cassini spacecraft
    • Gallery: Mission to Saturn
    • Lord of the Ringsexternal link

    (CNN) -- The spacecraft Cassini is sending back the finest images ever captured of Saturn's rings, giving scientists new insights into the planet, the origin of our solar system and even the formation of galaxies.

    "They are a treasure trove," said Cassini scientist Bonnie Buratti, who will use the spacecraft for visual infrared mapping.

    The rings -- the brightest in the solar system -- extend for hundreds of thousands of kilometers around the planet. They are composed of swarms of dust particles, tumbling rocks and icebergs of frozen water.

    "I don't think you have to be a ring scientist to appreciate this," said Carolyn Porco, a member of Cassini's imaging team. "I'm blown away."

    The highest resolution images of the rings will come in Thursday as Cassini continues its orbit around the distant planet. The most recent visits by two Voyager spacecraft during the early 1980s produced grainier images.

    "One of the most fundamental questions we want to answer during this mission [is] the relationship between the rings and the satellites," Buratti said.

    Scientists believe that Saturn's rings will refine models explaining how the planets -- and even galaxies -- coalesced from the diffuse clouds of gas and particles in the early universe.

    Scientists are poring over new images that Cassini is sending back during its first of 76 scheduled orbits.

    The intrepid spacecraft shot through a gap in the rings on Wednesday night to become the first spacecraft to enter Saturn's orbit.

    "We'll learn more about the relationship between the rings and satellites...and a lot of the models that will be tested also apply to galactic formation and the origin of our solar system," Buratti said.

    Saturn's rings are thought to have originated relatively recently -- from 10 million to 100 million years ago -- following a huge orbital collision. The massive impact of a satellite around Saturn and the smaller, subsequent collisions probably led to the planet's rings, although astronomers cannot be sure.

    Saturn boasts the largest rings in the solar system, according to The Universal Book of Astronomy, outshining those of all three other giant planets: Jupiter, Uranus and Neptune. The seven main rings are denoted by the letters A through G.

    Although the rings are only about 1.5 kilometers high, they are extremely wide -- more than 170,000 kilometers if taken together. Yet their mass would account for barely 1 percent of Earth's moon and measure just 100 kilometers across.

    The gaps in the rings that give Saturn its distinctive appearance are caused by gravitational tides that pull on the debris, as well as smaller satellites which clean up certain orbits by "vacuuming" smaller particles.

    Cassini used one of the outer gaps to enter orbit. The spacecraft is named for 17th century Italian-born French astronomer Jean-Dominique Cassini, who discovered a major gap in the rings, since known as Cassini's division.

    The trail-blazing spacecraft may reveal more about long-standing mysteries of the rings during its four-year mission.

    Dark radial markings, called spokes, and the F-Ring, with a braided structure with what appear to be "knots," have long intrigued astronomers. Cassini is expected to relay about 300,000 images during the next four years.

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