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Periodic features in Saturn's F ring: evidence for nearby moonlets


THE Voyager 1 and 2 spacecraft1,2 found that the F ring of Saturn contains a remarkable diversity of features, from kinks and clumps to the so-called braids, with typical longitudinal spacings estimated to range from 5,000 to 13,000 km. Because any nearby satellite perturbing a narrow ring should produce periodic features of a single wavelength3–5, the F ring's 'shepherd' satellites, Prometheus and Pandora, have been suspected to cause the observed periodicities. To test this simple idea, we have now examined a selection of the best available Voyager images of Saturn's F ring by applying a fast Fourier transform technique to azimuthal profiles from spacecraft ring images. Only a few distinct periodic signals, including one due to the inner shepherd, are visible. We suggest that these periodic signatures provide evidence for so-far-undiscovered satellites next to this puzzling ring.

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Kolvoord, R., Burns, J. & Showalter, M. Periodic features in Saturn's F ring: evidence for nearby moonlets. Nature 345, 695–697 (1990).

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