NASA - National Aeronautics and Space Administration

Now that Spirit and Opportunity have discovered evidence that liquid water existed on Mars, our Solar System is a little less mysterious. Right?

Not by a long shot. The greatest questions have yet to be answered, and here's one of the greatest: What's the story with Saturn's rings?

Sure, Jupiter, Neptune, and Uranus all have ring systems that we've detected in the last half century, but for over 400 years now, we've been wondering: What's the story with Saturn's rings?

The answer is Cassini-Huygens. The international spacecraft was launched in 1997, and is now only two and a half months away from reaching Saturn.

Image to right: Saturn, as seen from the Cassini-Huygens spacecraft on its approach to the ringed planet. Credit: NASA.

Cassini, the orbiter component of the spacecraft, will spend four years circling the planet and sending back volumes of data on Saturn and its rings. The Huygens component of the spacecraft will take a more hands-on approach and descend onto the surface of one of Saturn's moons, named Titan, in January of 2005.

But back to the rings. A lot of good theories have been provided over the years, but just when we think we've got an answer, we get another question mark.

Saturn's spokes are one of the biggest question marks. The planet's ring system is divided into three main sections: A, B and C. Dark spots were seen on Ring B in images sent back from Voyager 1 and 2 in the early 1980s. Photographs taken by Cassini-Huygens on its way to Saturn show no evidence of the spokes still existing, puzzling astronomers and creating even greater mystery behind them.

Image to left: Voyager 2 snapped this image of spokes in Ring B during its flyby in 1981. Credit: NASA.

Clumps seen in the rings are another mystery all together. The Voyager missions detected large particles in Saturn's F ring, conflicting with certain theories behind the ring system's formation. Images recently taken by Cassini-Huygens as it approaches the planet confirms that the clumps are still there, and astronomers are looking forward to receiving the highest resolution images ever taken of the rings as it reaches Saturn.

Expect new theories on both spokes and clumps this summer, as Cassini-Huygens achieves orbital insertion on July 1.

+ NASA's Cassini-Huygens Web site
Matthew Cavagnaro
NASA's John F. Kennedy Space Center