An article published in the journal “Nature Astronomy” reports a study on the planet Saturn’s core. Caltech astronomers Christopher Mankovich and Jim Fuller analyzed data collected by the Cassini space probe on the oscillations of Saturn’s rings caused by the internal seismic activity to indirectly analyze the characteristics of the planet’s interior. The conclusion is that the core is not rocky but a mixture that has been compared to a soup or a sludge composed of ice, rock, and metallic fluids that fill a volume for about 60% of Saturn’s diameter, far more than it was previously estimated.
The mission of the Cassini space probe ended on September 15, 2017, but the enormous amount of data collected over years of work remains available and will be used for various types of research for who knows how many years to come. The idea of using Saturn’s rings as a sort of cosmic seismograph to study the planet’s interior is anything but new, as it was first reported in the 1990s to be applied years later thanks to the data collected by Cassini.
Dr. Christopher Mankovich explained that Saturn has continuous but subtle seismic activity. The planet’s surface moves about one meter every one or two hours, and the rings oscillate due to the tiny gravitational changes that are generated by that activity.
The analysis of the collected data offers some information on Saturn’s core. There are discussions about the nature of the cores of gas giant planets, and according to some theories they are rocky. However, this study led Christopher Mankovich and Jim Fuller to conclude that Saturn’s core is more complex. That’s because descending deeper, hydrogen and helium gases gradually mix with an increasing amount of ice and rock as they move towards the center of the planet.
The frequencies of the ring oscillations allow deducing the formation of the planet’s layers. The analysis of the data indicates that the interior must be stable and the core is made up of a mass about 55 times the Earth’s composed of ice and rock for about 17 earth masses and the rest of a fluid of hydrogen and helium that at those conditions behave like metals. This means that the core occupies a volume of about 60% of the diameter of Saturn.
There is no definite boundary between what was compared to a soup or sludge of core materials and the rest of the planet. For this reason, the core has been called “fuzzy” in jargon. Recent research indicates that Jupiter may also have such a core, so this research helps to better understand the structure of gas giant planets.
These recent findings regarding gas giant cores have implications for their formation as well. In the current model, the formation starts from a rocky core that attracts large quantities of gas but if these planets’ cores are fuzzy, it’s possible that the gas gets incorporated into them in the early stages of formation. In short, these are discoveries that will be further analyzed and other studies will be conducted to better understand how gas giants form.
