A new paper suggests Saturn’s core is more like a fluid than a solid, and makes up more of the planet’s interior than we thought. From a report: With its massive rings stretching out 175,000 miles in diameter, Saturn is a one-of-a-kind planet in the solar system. Turns out its insides are pretty unique as well. A new study published in Nature Astronomy on Monday suggests the sixth planet from the sun has a “fuzzy” core that jiggles around. It’s quite a surprising find. “The conventional picture for Saturn or Jupiter’s interior structure is that of a compact core of rocky or icy material, surrounded by a lower-density envelope of hydrogen and helium,” says Christopher Mankovich, a planetary scientist at Caltech and coauthor of the new study, along with his colleague Jim Fuller.
What Mankovich and Fuller glimpsed “is essentially a blurred-out version of that conventional structure.” Instead of seeing a tidy boundary dividing the heavier rocks and ice from the lighter elements, they found that the core is oscillating so that there is no single, clear separation. This diffuse core extends out to about 60% of Saturn’s radius — a huge leap from the 10 to 20% of a planet’s radius that a traditional core would occupy. One of the wildest aspects of the study is that the findings did not come from measuring the core directly — something we’ve never been able to do. Instead, Mankovich and Fuller turned to seismographic data on Saturn’s rings first collected by NASA’s Cassini mission, which explored the Saturnian system from 2004 to 2017.
“Saturn essentially rings like a bell at all times,” says Mankovich. As the core wobbles, it creates gravitational perturbations that affect the surrounding rings, creating subtle “waves” that can be measured. When the planet’s core was oscillating, Cassini was able to study Saturn’s C ring (the second block of rings from the planet) and measure the small yet consistent gravitational “ringing” caused by the core. Mankovich and Fuller looked at the data and created a model for Saturn’s structure that would explain these seismographic waves — and the result is a fuzzy interior. “This study is the only direct evidence for a diffuse core structure in a fluid planet to date,” says Mankovich.
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