Saturn Ring Rain is Greater Than Previously Thought

Posted on April 10, 2013

A new study has found that there are more charged water particles falling into the atmosphere of Saturn from its rings than previously thought. The study was led by researchers from the University of Leicester, England and funded by NASA. The study found the rain influences the composition and temperature structure of parts of Saturn's upper atmosphere. Scientists say it also quenches the ionosphere of Saturn. The illustration above shows how charged water particles flow into the Saturnian atmosphere from the planet's rings, causing a reduction in atmospheric brightness. A larger version of the image can be found here.

James O'Donoghue, the paper's lead author and a postgraduate researcher at Leicester, said in a statement, "Saturn is the first planet to show significant interaction between its atmosphere and ring system. The main effect of ring rain is that it acts to 'quench' the ionosphere of Saturn. In other words, this rain severely reduces the electron densities in regions in which it falls."

Images from NASA's Voyager spacecraft in the 1980s showed two to three dark bands on Saturn. Scientists theorized at the time that water could have been showering down into those bands from Saturn's rings. These bands were again observed on the planet in near-infrared wavelengths with the W.M Keck Observatory on Mauna Kea, in Hawaii, in April 2011.

The researchers determined that charged water particles from the Saturn's rings were being drawn towards the planet along Saturn's magnetic field lines and neutralizing the glowing triatomic hydrogen ions. This leaves "shadows" in what would otherwise be a planet-wide infrared glow. The scientists say the shadows cover some 30% to 43% of Saturn's upper atmosphere surface from around 25 to 55 degrees latitude. The researchers say this is a significantly larger area of ring rain than suggested by the 1908s images from NASA's Voyager mission.

The research paper was published here in the journal, Nature.

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