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Cassini Starts Saturn Grad School

Irene Klotz, Discovery News

The Cassini team plans to hone in on Enceladus during the extended mission, with seven flybys scheduled over the next two years. Scientists would love to discover what is powering Enceladus' geysers. Among the contenders: radioactive isotopes and tidal forces.

"There's not a good story yet," Hansen-Koharcheck said. "It's one of those science questions that people love to work on because it's hard, it's a challenge."

Scientists also want to use Cassini to explore if another moon Dione has similar, but much less powerful, geyser-like activity and also if the moon Rhea does indeed have rings.

Delayed Retirement

Cassini's extended mission occurs as Saturn shifts in position so that the sun passes through equinox in August 2009.

The alignment creates a window of opportunity for detailed studies of Saturn's rings with sunlight passing directly through the plane of the rings. Eventually the ring shadows will slip past the equator and fall into the southern hemisphere as the sun moves northward, relative to Saturn.

The perspective will be similar to the view of Voyager as flew by Saturn 29 years ago.

Scientists plan to use Cassini to assess ring structure and composition and to test a new theory that the rings are continually reforming from old material.

On Saturn itself, scientists want more information about a storm that has been sitting on the planet's south pole for the last 50 years.

"The phenomenon is not understood," Mitchell said.

Already, scientists are looking ahead to a Cassini follow-on mission after the two-year extension and an eventual plunge from orbit to avoid contaminating any possible indigenous life that may exist on a moon or elsewhere in the Saturn system.

One idea is to fly Cassini through a gap between Saturn and its innermost ring, a risky maneuver that could be its final contribution to science.

Already, Cassini is laying the groundwork for a successor probe. NASA is considering destinations for a new outer planet mission and while Jupiter's moon Europa, which has an underground ocean, remains a top contender, the Cassini team is building a case for Titan, where, as Mitchell put it, "The things of interest are sitting on the surface."

Related Links:

Irene Klotz's blog: Space Diary

Discovery Space

NASA's Cassini Mission

Saturn Stats

How Stuff Works: Saturn Explained