Planetologists found a link between Saturn's rings and the size of the planet's core. Credit: NASA/JPL/Space Science Institute

Saturn’s Rings Reveal Clues About Gas Giant’s Core

The theory that fluctuations in the gravitational field of Saturn can create vibrations in its rings, which makes them a kind of seismograph for studying the structure of the gas giant, first appeared in the early 1990s.

Planetologists revealed the results of a new study on Cassini’s archived observations of Saturn’s rings. Scientists were able to give more accurate estimates of the size and mass of Saturn’s core by analyzing the vibrations in its rings caused by fluctuations in the planet’s gravitational field. It turned out that the radius of the core can be almost 60 percent of the radius of the gas giant, while a third of its mass is made up of rocks and ice. 

Saturn’s rings reveal new information about the planet’s core

Internal structures

Scientists obtain the most accurate constraints on the model of the internal structure of giant planets in the course of studying their gravitational fields.

Atmospheric processes

However, the results of such studies are strongly influenced by processes in the atmospheres of planets, which makes it difficult to accurately measure the mass and size of the nuclei of Jupiter and Saturn.

The gravitational field of Saturn

The theory that fluctuations in the gravitational field of Saturn can create vibrations in its rings, which makes them a kind of seismograph for studying the structure of the gas giant, first appeared in the early 1990s.

Confirming the theory

In 2013. the theory was confirmed by data from the Cassini interplanetary station, which in the course of observations of the C ring, revealed density waves in it, which were different from other waves in the rings caused by gravitational interactions with the satellites of Saturn.

Gravitational waves

Oscillations of the f-mode type were mainly recorded, but internal gravitational waves (g-modes) were also recorded, which carry information about the internal structure of the planet.

Saturn’s rings and internal structure

Christopher R. Mankovich and Jim Fuller of the California Institute of Technology used Cassini’s archived observations of Saturn’s rings to build a new model of Saturn’s internal structure.


Scientists have come to several conclusions. If the core is considered as a region containing half of the planet’s heavy elements, then its effective radius is 0.32 of the radius of Saturn, but if there is a stable boundary between the core and Saturn’s envelope, in which hydrogen predominates, then the radius of the core is 0.59 of the radius of Saturn.

Mass of the core

At the same time, the mass of the core was estimated at 55.1 masses of the Earth, of which 17.4 masses of the Earth are rocks and ice.


The researchers note that these estimates of the mass and radii of the nucleus are significantly larger than the previous ones. The boundary between Saturn’s core and shell appears to be a diffuse, layered region that delays the planet’s cooling rate, helping to explain Saturn’s surprisingly high luminosity.

More about Saturn

Earlier this year, we talked about another curious study focused on Saturn’s atmosphere which summarized three years of observations. Results showed incredible changes in Saturn’s equatorial clouds and winds, as well as in the northern polar region. Read all about it here.

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Andrews, R. G. (2021, August 16). Saturn’s rings are like a seismometer that reveal the planet’s core. The New York Times.
Drake, N. (2021, August 16). Ripples in Saturn’s RINGS reveal the planet’s Giant, slushy core. Science.
Mankovich, C. R., & Fuller, J. (2021, August 16). A diffuse core in Saturn revealed by RING SEISMOLOGY. Nature News.
Pultarova, T. (2021, August 16). Saturn’s rippling rings point to MASSIVE, soupy core hidden inside.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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