Waves in Saturn’s Rings Reveal Its Fuzzy Core of Ice

While astronomers often rely on the gravitational pull of a planet to determine the size and makeup of its core, there are other ways to make those guesstimates. In the case of Saturn, for example, astronomers say they’ve detected waves in the planet’s rings that betray a planet core of ice and rocks; one that’s diffuse ( or “fuzzy”), brimming with hydrogen and helium, and 55 times as massive as Earth.

A pair of Caltech scientists say that, based on seismic waves in its rings, Saturn likely has a fuzzy planet core made of ice, rocks, and lots of helium and hydrogen.


Science News reported on this latest look into Saturn’s core. A pair of scientists at Caltech, astronomer Christopher Mankovich and astrophysicist Jim Fuller, identified the waves in Saturn’s rings. The duo, who were aiming to ascertain the structure of Saturn’s core, compared gravitational models with the observed seismic measurements; using the latter to confirm which version of the former is most accurate.

Upon comparison, Mankovich and Fuller found evidence of a core unlike those in the most popular standing models. Instead of a lump of ice and rock surrounded by gases, the duo observed seismic ring waves that would result from a scattered core. A scattered core consisting of pieces of ice and rock, with lots of gasses in between them.

In a tweet from 2020 (above), Mankovich provides an exaggerated visualization of the seismic waves in Saturn’s rings. Note that Saturn’s gravitational field variations, which result from oscillations in its core, produce the waves.

Based on their ring-wave data, Mankovich and Fuller estimate Saturn’s core takes up approximately 60% of the planet’s radius. The core also has roughly 17 Earth masses of ice and rock, with the remaining mass split between the hydrogen and helium. The scientists also say Saturn’s core is stably stratified; meaning it has distinct layers that have varying levels of heavy elements. (With the centermost layers having the most heavy elements.)

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In the study outlining their findings in the journal Earth and Planetary Astrophysics, Mankovich and Fuller say this type of core “may reflect [Saturn’s] primordial structure,” as well as how it’s accreted mass over time. It could also help to illuminate the strange phenomenon wherein Saturn gives off more heat than it receives from the Sun. It turns out the planet’s “fuzzy” core may be the exact thing that’s keeping it so toasty.

Feature image: Judy Schmidt

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