| News / Space News |
At Saturn, One of These Rings is not like the Others
NASA | SEPTEMBER 28, 2015
In a recent study, a team of Cassini scientists reported that one section of the rings appears to have been running a slight fever during equinox. The higher-than-expected temperature provided a unique window into the interior structure of ring particles not usually available to scientists.
The planet Saturn, viewed by NASA's Cassini spacecraft during its 2009 equinox. 
The researchers examined data collected by Cassini's Composite Infrared Spectrometer during the year around equinox. The instrument essentially took the rings' temperature as they cooled. The scientists then compared the temperature data with computer models that attempt to describe the properties of ring particles on an individual scale.
What they found was puzzling. For most of the giant expanse of Saturn's rings, the models correctly predicted how the rings cooled as they fell into darkness. But one large section -- the outermost of the large, main rings, called the A ring -- was much warmer than the models predicted. The temperature spike was especially prominent in the middle of the A ring.
The team's analysis suggested the best explanation for the A ring's equinox temperatures was for the ring to be composed largely of particles roughly 3 feet (1 meter) wide made of mostly solid ice, with only a thin coating of regolith.
The accumulation of dense ring particles in one place suggests that some process either placed the particles there in the recent geologic past or the particles are somehow being confined there. The researchers suggest a couple of possibilities to explain how this aggregation came to be. A moon may have existed at that location within the past hundred million years or so and was destroyed, perhaps by a giant impact.
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