It seemed so obvious to me I never really gave it much thought, but really, how do you measure the rotation of a gas planet? After all, there's nothing fixed on the surface. In the case of Saturn, the problem is actually quite vexing:

Using data collected by NASA's Cassini, Pioneer and Voyager spacecraft, scientists have revised the ringed planet's rotation period to 10 hours, 32 minutes and 35 seconds-about 15 minutes shorter than an estimate made only last year.

Those precious minutes could have big implications for how scientists think about Saturn and other gas giants.

"While that may seem like a small uncertainty for the average person, it makes an enormous difference in terms of how we can understand the interior of Saturn," said study team member Gerald Schubert of the University of California, Los Angeles.

It's not as if we can throw a plum bob down there, ya know?