Researchers have unveiled the clearest images yet of the massive cyclone that revolves over Saturn‘s south pole, and revealed that the southern storm is matched by an equally powerful cyclone at the planet’s north pole. Time-lapse images, taken by the Cassini spacecraft, show that the northern cyclone has wind speeds of 325 miles per hour, more than twice as fast as Earth’s strongest hurricanes. Says Cassini scientist Kevin Baines: “In a lot of ways, these are the most powerful cyclones ever seen…. They would expand over the whole planet if it was the Earth” [Discovery News].
The source of heat that powers these massive storms is not yet clear; Earth’s cyclones draw heat from the oceans that they drift across, but Saturn’s fixed cyclones have no bodies of water at their bases. They may be driven by Saturn’s internal heat, which can create giant weather patterns by causing massive parcels of atmospheric gases, most likely ammonium hydrosulfide, to rise and fall. It’s also possible that sunlight trapped in the planet’s atmosphere could drive the motions [Science News].
Cassini took the northern images using infrared light, because the north pole is currently too dark for visible-light cameras. The images show the glow generated by the planet’s internal heat as lighter patches, with the thick clouds that block those infrared waves appearing as dark bands. The southern cyclone was pictured in both infrared and visible light, and the sharp images reveal new details of the vortex, including an inner ring of storm clouds. Says Cassini scientist Tony DelGenio: “What looked like puffy clouds in lower resolution images are turning out to be deep convective structures seen through the atmospheric haze” [SPACE.com].
The images were released only days after Cassini made an impressive swoop past the Saturnian moon Enceladus, dipping down to within 16 miles of the surface to analyze the plumes of water vapor that jet up from cracks in the moon’s icy surface. Cassini will spend at least two more years studying Saturn and its strange moons; its next immediate mission is another flyby of Enceladus at the end of October. Researchers also plan to continue studying Saturn’s cyclones as the planet’s seasons change.
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Image: NASA/JPL/University of Arizona