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A Statistical Analysis of Spokes in Saturn’s B-Ring

Presentation #112.07 in the session Many Planets, More Rings (Oral Presentation)

Published onOct 23, 2023
A Statistical Analysis of Spokes in Saturn’s B-Ring

Spokes in Saturn’s B ring, dusty radially-oriented features discovered by the Voyager spacecraft over 40 years ago, remain a mystery. They appear, evolve, and disappear seemingly at random but with tantalizing clues that have suggested that spokes are seasonal, that electromagnetic forces are at play, and that Saturn’s shadow is important. Over the years, we have developed a collisional cascade model for the origin and evolution of B ring spokes and we seek to test this model and others against the extensive set of ring images returned by the Cassini spacecraft. Accordingly, we have undertaken a comprehensive analysis of all Cassini images of Saturn’s B ring, focusing on the ghostly spokes. Our goals are i) to identify all spokes in all images and ii) to characterize their properties including areal coverage, radial extent, and brightness. As there are ~10,000 relevant images, far too many to reduce by hand, we employ computer algorithms to both identify spokes automatically and to compile statistics on them. We have built two data reduction pipelines: one with a standard approach primarily utilizing pixel-to-pixel brightness variations and a second which employs machine learning. Both approaches successfully identify most spokes in most images, but each approach has its own advantages and its own problems. By comparing the output from the two pipelines we have been able to refine each approach and we have seen the output from the two pipelines converge. This gives us increased confidence in the correctness and robustness of our identifications. We will present the statistics that we have compiled on all spokes in the entire Cassini B-ring data set and will discuss the implications of these results for spoke formation models.

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