An article published in the journal “Nature Communications” reports a study on the stratification of the hexagonal structure of the gigantic hurricane that occupies the planet Saturn’s north pole. A team of researchers led by Professor Agustín Sánchez-Lavega of the University of the Basque Country used data collected by the Cassini space probe and the Hubble space telescope to understand that it’s a system composed of at least seven layers of haze with an extension of over 300 kilometers. The study also allowed to discover that those layers contain microscopic frozen particles composed of hydrocarbons such as acetylene, propane, propine, diacetylene, and butane.
Discovered thanks to the Voyager space probes in 1980, the hexagonal structure immediately aroused the interest of scientists belonging to various disciplines for its characteristics. A central storm surrounded by a series of vortices that form a stable structure with a width of about 30,000 kilometers is something truly extraordinary. The Cassini space probe, whose mission ended on September 15, 2017, captured many images of that hexagon that allowed to study the atmospheric phenomena in progress and to understand which compounds are present. Now a new research went further to get more comprehensive answers.
The information gathered from Saturn’s orbit is precious, and only a space probe sent to study the planet up close could get it. That doesn’t mean that the observations made from the Earth or its orbit are useless, on the contrary a different point of view obtained with different instruments can offer a more complete portrait of the hexagonal structure.
In 2015, the Cassini space probe took high-resolution photos observing Saturn’s atmosphere just above the horizon, allowing to observe the layers of clouds above the hexagon distinguishing details one or two kilometers wide. Those photos were taken using different filters that allowed to separate the ultraviolets from the infrareds. Just 15 days later, the Hubble Space Telescope observed the hexagon from above, allowing to obtain information that complemented Cassini’s.
By studying the images of Cassini and Hubble, the researchers found that the hexagon is composed of a series of layers, at least seven, which are between 7 and 18 kilometers thick. The image (Courtesy of the Basque Country University) shows the hexagon and its layers. They’re composed of hazes since they contain microscopic particles of hydrocarbons which, at temperatures between -120° and -180° Celsius, are frozen. Those hydrocarbons can be acetylene, propane, propine, diacetylene, and even butane in the highest clouds.
The layers that make up the hexagon are regular and to explain it, the researchers proposed an analogy with phenomena known on Earth, albeit on a much smaller scale, and on other planets. Probably those layers are formed by the vertical propagation of gravity waves that produce oscillations in the density and temperature of Saturn’s atmosphere. The hexagon itself and its powerful jet stream could be responsible for those gravity waves.
Similar phenomena have been observed on Earth, but the scale of the Saturn hexagon with its peculiarities make it unique. Continuing research to better understand the processes in progress will help improve certain models in the field of fluid dynamics that might be applied to other phenomena.
