Short-Term Flings at Saturns Rings
The Saturn system is assumed to be 4.5 billion years old like the rest of the solar system. What mean the delicate dances of ring particles that have been observed by Cassini lately? One would think moons and particles had pretty much settled into a stable old age by now, but no: some things change on a daily basis, and Cassini’s cameras are catching the action. The question is, how long can this go on? Is the dance marathon at Saturn setting new records?
A Cassini press release shows gouges in the narrow F-ring that scientists say are evidence of a collision. And just a couple of days earlier, another Cassini press release published pictures of delicate ring arcs among two of Saturn’s small moons, Anthe and Methone. “This is further evidence that most of the planet’s small, inner moons orbit within partial or complete rings,” the article says. Are they exceptions to a rule of stability and senescence? No again; “The intricate relationships between these ring arcs and the moons are just one of many such mechanisms that exist in the Saturn system.”
Update 09/18/2008: Another Cassini press release shows the G-ring arc rounding the ansa. The article describes the destructive processes at work: “Micrometeoroids collide with the large particles, releasing smaller, dust-sized particles that brighten the arc. The plasma in the giant planet’s magnetic field sweeps through this arc continually, dragging out the fine particles and creating the G ring.”
Notice how rarely the scientists ever address the age question. It seems hard to believe that interactions this delicate and dynamic could persist for billions of years. Before spacecraft got there, scientists expected things to be simple and stable and old. Things like ring arcs, thousands of ringlets, ring spokes and ring collisions caught them by complete surprise. Why are they silent on the question about whether such phenomena could last that long? As with biological evolution, the answers are worded as vague promissory notes: “Understanding these interactions and learning about their origins can help us to make sense of what we are seeing in the Cassini images.” They need help, all right, especially with sense.