Happy Nice Mall

This diffuse core extends to about 60% of Saturn’s radius – a huge leap from 10% to 20% of a planet’s radius that a conventional core would cover.

One of the craziest aspects of the study is that the findings didn’t come directly from measuring the core—something we could never do. Instead, Mankovich and Fuller turned to seismographic data about Saturn’s rings first collected by NASA’s Cassini mission, which surveyed the Saturn system from 2004 to 2017.

“Saturn actually always rings like a bell,” Mankovich says. As the core shakes, it creates gravitational perturbations that affect the surrounding rings, creating subtle “waves” that can be measured. As the planet’s core oscillates, Cassini was able to examine Saturn’s C ring (the second block of rings from the planet) and measure the small but consistent gravitational “ringing” caused by the core.

Mankovich and Fuller looked at the data and created a model for Saturn’s structure to explain these seismographic waves, and the result is a fuzzy interior. “This work is the only direct evidence to date of a diffuse core structure on a fluid planet,” Mankovich says.

Mankovich and Fuller think the reason the structure works is because the rocks and ice near the center of Saturn are soluble in hydrogen, allowing the core to behave like a liquid rather than a solid. Their model suggests that Saturn’s scattered core contains rocks and ice that make up more than 17 times the mass of the entire Earth – so there’s so much material bobbing around.

A scattered core can have several major effects on how Saturn works. Most importantly, it stabilizes some of the interior against convective heat, which would otherwise drive Saturn’s interior into turbulence. In fact, this stabilizing effect gives rise to internal gravitational waves affecting Saturn’s rings. What’s more, the diffuse core would explain why Saturn’s surface temperatures are higher than traditional convective models suggest.

Still, Mankovich acknowledges that the model is limited in some important ways. It cannot explain what scientists have observed about Saturn’s magnetic field, which is strange in many ways (for example, it exhibits an almost perfect symmetry on its axis that is quite unusual). He and Fuller hope that future research can confine the interior more narrowly and give scientists clues as to how the planet’s core might affect the magnetic field.

They also hope that NASA’s Juno mission can reveal a similar diffuse core on Jupiter. This would go a long way to confirming suspicions that when giant planets form, the process naturally creates gradients of materials rather than clean, solid cores. Some research using gravitational data collected by Juno seems to support this idea as well.