Solar System Chatter

Smithsonian Voices Solar System Chatter

Lighter Rings, Lagging Spring

Astronomers have discovered that Saturn’s rings don’t always seem to have as much material as they appear to. Using Cassini’s measurements of spiral density waves (some particles, perturbed by gravity from nearby moons, travel faster than others through the rings, creating a wave), scientists discovered that Saturn’s B ring has far less mass than expected. The math shows that even though parts of the B ring are nearly 10 times more opaque than the A ring, it’s only two or three times more massive. A less massive ring would evolve faster, which means the B ring might be much younger than previously thought.

Meanwhile, scientists are learning a lot about Titan (silhouetted above) as Saturn continues on its 30-year orbit around the sun. Cassini has been able to observe the unusual moon with the thick atmosphere for the last 10 years, while the seasons have changed from early winter to late spring. Cassini observations show one expected result: the latitude with the warmest temperatures (still a frigid -240 degrees Fahrenheit) shifted north as spring approached. But more unusual was that the northern hemisphere seemed a bit slow to warm up based on climate models. Scientists believe that has to do with Titan’s methane seas, which cover about 10 percent of the hemisphere, in the polar region. It’s taking the seas longer to warm up, and so the region lags behind with it.