The Scientific Tour de Force Continues

Todd J. Barber, Cassini lead propulsion engineer

While Cassini's flight team enjoyed a brief break during solar conjunction, the spacecraft itself continued its scientific tour de force before, during, and after. Nearly a month ago, our imaging instruments took almost half a day to search for elusive "spokes"-- dark, radial features within or near Saturn's rings. I remember seeing spokes for the first time over a quarter century ago, surely one of the most perplexing of Voyager's results at Saturn as brilliantly revealed in the pages of "National Geographic." We predict these features will become more prevalent as the geometry of the rings with respect to the sun changes in the coming years.

Cassini also has been observing Saturn itself, mounting a coordinated effort to unlock the mysteries of the north polar region. Any one instrument helps reveal a piece of the puzzle, but only by assembling the puzzle pieces back on Earth can we truly understand the complexities of localities like Saturn's north pole. Perhaps in the interest of hemispherical fair play, Cassini also searched for aurora near Saturn's southern pole. Observations of a lovely crescent Rhea and its dark side closed out August, along with movies of Saturn's kinked F-ring and infrared observations of Titan to help reveal surface composition. What a way to go into solar conjunction!

Another pivotal discovery occurred within the last few weeks, indeed this one worthy of a press release. Our tireless explorer discovered faint ring arcs acting as bookends for two of Saturn's tiny moons, Anthe and Methone. As with spokes, the ring arcs discovered by Voyager 2 at Neptune are among my favorite of solar system surprises, for just as spokes should shear apart in rotating ring systems, ring arcs should quickly spread out and form a uniform ring. Apparently, a gravitational resonance with Saturn's twin of the "Death Star," Mimas, helps keep these ring arcs stable. Nature isn't always as symmetrical and orderly as our simplified models predict--and that's one of many reasons planetary science is so, well, heavenly.