For a rocky planet, it can be easy to determine the length of a day. Just pick a reference point and watch how long it takes for the camera to disappear. But for planets like Saturn it's not that easy. There are no surface features to track.
Scientists have spent decades trying to determine the Saturn rotation period. But the gas giant did not want to reveal its secrets. A new study in AGU's Journal of Geophysical Research: Space Physics could finally give the answer. The study is titled "Saturn's Multiple, Variable Periodicities: A Dual Flywheel Model of Thermosphere-Ionosphere-Magnetosphere Coupling."
For a planet like Earth, we know what we measure when we measure the rotation period. We measure the surface of the planet. But for a gas giant, things are more complex. Which layer of the planet are scientists talking about?
Saturn is a multi-layered gas giant, probably with a rocky core. This core is surrounded by a layer of ice, then by metallic hydrogen and helium. Then an area of helium rain, further surrounded by a region of liquid hydrogen. Then comes a large area of gaseous hydrogen. The upper atmosphere of Saturn consists of three layers: At the top are ammonia clouds, including ammonium hydrogen sulfide, and below them water vapor clouds.