Subtle ripples in Saturn’s innermost rings indicate the planet’s core is not a compact, solid structure as some have theorised but more like a thick “soup” of ice, rock and metallic fluids extending across 60 percent of the planet’s diameter.
The sludge-like “fuzzy” core sloshes about ever so slightly as the planet rotates, causing fluctuations in Saturn’s gravitational field that set up tell-tale spiral patterns in its innermost rings.
“We used Saturn’s rings like a giant seismograph to measure oscillations inside the planet,” said Jim Fuller, assistant professor of theoretical astrophysics at Caltech and co-author of a paper in Nature Astronomy. “This is the first time we’ve been able to seismically probe the structure of a gas giant planet, and the results were pretty surprising.”
The findings, based on data collected by NASA’s Cassini spacecraft, are the best evidence yet of a fuzzy core and are in step with recent observations by NASA’s Juno probe of a similar “diluted” core below Jupiter’s cloudtops.
Lead author Christopher Mankovich, a postdoctoral scholar research associate in planetary science, said fuzzy cores “are like a sludge.”
“The hydrogen and helium gas in the planet gradually mix with more and more ice and rock as you move toward the planet’s centre,” he said. “It’s a bit like parts of Earth’s oceans where the saltiness increases as you get to deeper and deeper levels, creating a stable configuration.”
He said Saturn is “always quaking, but it’s subtle.”