Uncovering Peculiar Rainbows: A Catalogue-Scale Survey of Luminous Bands in Saturn's E Ring

Saturn's E ring harbours faint, quasi-periodic, inclined brightness structures called luminous bands, first characterised from Cassini VIMS and ISS observations during Enceladus flybys. We present the first automated, catalogue-scale survey of luminous bands, drawing on 23 Cassini flyby sequences spanning 2006–2012. Detection exploits the chromatic character of the bands by subtracting a broadband CLEAR-filter image from its science-filter counterpart to isolate wavelength-dependent brightness variations. Their quasi-periodic, inclined nature motivates a frequency-domain search using a zero-padded two-dimensional Fourier angular spectrum, with candidates assessed against a phase-randomised null ensemble. Of 573 processed images, 62 yield positive detections across eight encounter sequences. Six carry no prior published detection, including the first ISS detection for E13, and five are non-targeted flybys, demonstrating bands are recoverable from archival data. The observed band directions are compared against a diffraction model: 39 of the 62 detections agree to within 2 degrees, confirming the grating interpretation. Band contrasts decrease with Cassini–Enceladus distance, suggesting the strongest structure near the plume source. Notably, no detections occur in the morning ansa despite comparable coverage. A complementary VIMS spectral analysis reveals selective suppression of sub-micron grains on the morning-side ring, consistent with size-selective electromagnetic clearing by Lorentz forces, explaining the asymmetric detection rate.