This diffuse core extends to about 60% of Saturn’s radius-a huge leap from 10% to 20% of the planet’s radius occupied by the traditional core.
One of the craziest aspects of the study is that these findings do not come from the core of direct measurement-something we have never been able to do. Instead, Mankovic and Fuller turned to Saturn’s ring seismic data first collected by NASA’s Cassini mission, which explored the Saturn system between 2004 and 2017.
“Basically, Saturn rings like a bell at all times,” Mankovic said. When the core swings, it creates gravitational disturbances that affect the surrounding ring, resulting in subtle “waves” that can be measured. When the planet’s core oscillates, Cassini is able to study Saturn’s C ring (from the planet’s second ring) and measure the small, consistent gravitational “ringing” caused by the core.
Mankovic and Fuller looked at the data and created a model of Saturn’s structure to explain these seismic waves—the result was an internal blur. “This study is the only direct evidence so far that there is a diffuse core structure in a fluid planet,” Mankovic said.
Mankovich and Fuller believe that the structure works because the rocks and ice near the center of Saturn are soluble in hydrogen, making the core behave like a fluid rather than a solid. Their model suggests that Saturn’s diffuse core contains rocks and ice, and its total mass is more than 17 times that of the entire Earth—so there is a lot of material swaying around.
The diffuse core may have some major effects on the way Saturn works. Most importantly, it can stabilize part of the interior to resist convective heat, otherwise it will disturb Saturn’s interior due to turbulence. In fact, this stabilizing effect produces internal gravity waves that affect Saturn’s rings. In addition, the diffuse core can explain why the surface temperature of Saturn is higher than the temperature suggested by traditional convection models.
Nevertheless, Mankovic acknowledged that the model has limitations in some important aspects. It cannot explain the scientists’ observations of Saturn’s magnetic field, and it is strange in many ways (for example, it exhibits almost perfect symmetry on its axis, which is unusual). He and Fuller hope that future research can restrict the interior more strictly and provide scientists with clues about how the core of a planet may affect its magnetic field.
They also hope that NASA’s Juno mission may reveal a similar proliferation core inside Jupiter. This will greatly help confirm the suspicion that giant planets were formed, a process that naturally produces material gradients rather than clean and solid cores.Some studies using gravity data collected by Juno Seems to support this idea.