Dr. Tom Stallard, Associate Professor in Planetary Astronomy at the University of Leicester and Dr. James O’Donoghue, who studied for his PhD at the University of Leicester, have found that Saturn’s rings are dying at the maximum rate estimated from Voyager 1 and 2 observations made decades ago.
The rings of ice are being pulled into Saturn by gravity as particles of ice under the influence of Saturn’s magnetic field.
O’Donoghue, who now works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “We estimate that this ‘ring rain’ drains the equivalent of an Olympic-sized swimming pool from Saturn’s rings in half an hour. The entire ring system will be gone in 300 million years.”
O’Donoghue believes that the rings could even disappear quicker than this. “Add to this the Cassini-spacecraft detected ring-material falling into Saturn’s equator, and the rings have less than 100 million years to live.” Although this sounds like a long time, it is comparatively short compared to Saturn’s age of over 4 billion years.
Stallard said: “The young age of the rings has some really startling implications. It is possible, in the age of the dinosaurs, that Saturn’s rings were even larger and brighter than we see them today. Something dramatic must have happened around Saturn to make them this large, long after the planet itself formed.”
The first hints that ring rain existed came from Voyager observations of a seemingly unrelated phenomena. These include changes in Saturn’s ionosphere, density variations in Saturn’s rings, and three narrow dark bands circling the planet at northern mid-latitudes. The three dark bands appeared in images of Saturn’s hazy upper atmosphere made by NASA’s Voyager 2 mission in 1981.
In 1986, Jack Connerney of NASA Goddard published a paper in Geophysical Research Letters that linked the narrow dark bands to the shape of Saturn’s magnetic field. This suggested that electrically-charged ice particles from Saturn’s rings were flowing down invisible magnetic field lines, and dumping water in Saturn’s upper atmosphere. The influx of water from the rings washed away the stratospheric haze, making it appear dark and producing the narrow dark bands captured in the Voyager images.
The next phase of O’Donoghue’s research will explore how the rings change according to changes in Saturn’s seasons.
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