EAVESDROPPING on Saturn's rings is revealing secrets of the gas giant's vast interior.
Conventional wisdom says that Saturn contains a solid central core surrounded by a roiling gassy-liquid mix of helium and hydrogen. "It's like a giant lava lamp – a slow boiling motion," says Jim Fuller of the Kavli Institute for Theoretical Physics in Santa Barbara, California. This flow was thought to keep everything evenly mixed.
But images captured by NASA's Cassini spacecraft revealed steady vibrations at six different places in Saturn's rings. Even though the rings are thousands of kilometres from Saturn's surface, vibrations in them correspond to the way the planet squishes and contracts.
Now Fuller has run a computer simulation of the vibrating rings. The results suggest that Saturn must have a stable, stratified layer, perhaps of liquid and rock, between the core and roiling exterior (Icarus, doi.org/vbh).
This is the first time a seismological investigation has been conducted on another planet. Future work should reveal more about the structure and evolution of gas giants.
This article appeared in print under the headline "To see inside Saturn, watch its rings"
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