Researchers have used new data from NASA's Cassini spacecraft to find out the length of a day on Saturn, which is 10 hours, 33 minutes and 38 seconds.

The answer was hidden in Saturn's rings, said a release from the NASA Jet Propulsion Laboratory on Friday.

Time on Saturn has eluded planetary scientists for decades, because the gas giant has no solid surface with landmarks to track as it rotates, and it has an unusual magnetic field that hides the planet's rotation rate.

During Cassini's orbits of Saturn, instruments examined the icy, rocky rings in unprecedented detail. Christopher Mankovich, a graduate student in astronomy and astrophysics at University of California, Santa Cruz, used the data to study wave patterns within the rings.

According to Mankovich's research published Thursday by Astrophysical Journal, he developed models of Saturn's internal structure that would match the rings' waves. It allowed him to track the movements of the interior of the planet and its rotation, offering evidence for more scientists to discover the length of one Saturn day.

His work determined that the rings respond to vibrations within the planet itself, acting similarly to the seismometers used to measure movement caused by earthquakes.

The interior of Saturn vibrates at frequencies that cause variations in its gravitational field. The rings detect those movements in the field, according to the research.

"Particles throughout the rings cannot help but feel these oscillations in the gravity field," Mankovich said. "At specific locations in the rings these oscillations catch ring particles at just the right time in their orbits to gradually build up energy, and that energy gets carried away as an observable wave."