资源环境科技发展态势分析平台

We present images of Saturn from the final phases of the Cassini mission, including images with 0.5 km per pixel resolution, as high as any Saturn images ever taken. Notable features are puffy clouds resembling terrestrial cumulus, shadows indicating cloud height, dome and bowl shaped cloud structures indicating upwelling and downwelling in anticyclones and cyclones respectively, and filaments, which are thread-like clouds that remain coherent over distances of 20,000 km. From the coherence of the filaments, we give upper bounds on the diffusivity and kinetic energy dissipation. A radiative transfer analysis by Sanz-Requena et al. (2018) indicates that methane-band imagery is most useful in determining cloud and haze properties in the 60-250 mbar pressure range. Our methane-band imagery finds haze in this pressure range covering 64 degrees-74 degrees planetocentric latitude. Filaments lie within the haze, and cumulus clouds lie below it, but pressure levels are uncertain below the 250 mbar level.

Plain Language Summary During its final half-year, the Cassini spacecraft took close-up images from 3000-4000 km above Saturn's cloud tops. The spatial resolution was as high as any images ever taken of the planet. They revealed isolated puffy clouds like terrestrial cumulus and also more exotic, threadlike clouds - filaments - that would stretch halfway around the Earth if they were on our planet. The filamentary clouds indicate that the level of turbulence in Saturn's atmosphere is very low. The images showed dome-shaped clouds indicative of upwelling at the centers of anticyclones and bowl-shaped clouds indicative of downwelling at the centers of cyclones.