Scientists know what time it is on Saturn


Using new data from NASA's Cassini spacecraft, researchers believe they have solved a longstanding mystery of solar system science: the length of a day on Saturn. It's 10 hours, 33 minutes, and 38 seconds.

The figure has decayed planetary scientists for decades, because the gas giant has no solid surface with traces of land as it rotates, and it has an unusual magnetic field that hides the planet's rotation rate.

The answer it turned out was hidden in the rings.

While Cassini's orbits of Saturn, instruments examined the icy, rocky rings in unprecedented detail. Christopher Mankovich, a graduate student in Astronomy and Astrophysics at Uk Santa Cruz, used data to study wave patterns within the rings.

His work determined that the rings respond to vibrations within the planet itself, acting directly on the seizures used to measure the movement caused by earthquakes. The interior of Saturn vibrates at frequencies that cause variations in its gravitational field. The rings, in turn, detect the movements in this field.

"Particles over the rings cannot help but feel the oscillations in the gravity field," saidankovich. "In specific locations in the rings, the oscillations bake ring particles at just the right time into their orbits to gradually build up energy, and the energy gets lost as an observable wave.

Mankovich's research, including January 17 by Astrophysical Journal, describes how he developed models of Saturn's internal structure that would match the waves. That allowed him to trace the movements of the interior of the planet – and thus its rotation.

The rotation rate of 10:33:38 indicates that the analysis yields several minutes faster than previous estimates in 1981, which are based on NASA's radio signals from the Voyager spacecraft.

Analysis of Voyager data, which is estimated to be 10:39:23 on the day, is based on magnetic field information. Cassini used magnetic field data as well, but earlier estimates ranged from 10:36 all the way to 10:48.

Scientists often rely on magnetic fields to measure planets rotation rates. Jipiter's magnetic axis, like Earth's, is not aligned with its rotational axis. So it swings around as the planet rotates, causing scientists to measure the periodic signal in the radio waves to get the rotation rate. However, Saturn is different. Its unique magnetic field is almost perfectly aligned with its rotational axis.

That is why the rings were key to homing at the length of the day. Saturn scientists are reluctant to have the best answer after such a central question about this planet.

"The researchers used waves in the rings to torture in Saturn interior, and to remove this long-sought, fundamental characteristic of the planet. And it's a really tough result," said Casinini Project Scientist Linda Spiler. "The ring considered the answer."

The idea that Saturn's rings could be used to study the cosmology of the planet was first suggested in 1982, long before the necessary observations were made.

Co-author Mark Marley, now in NASA Ames Research Center in California's Silicon Valley, subsequently flies out the idea for his Ph.D. In 1990 with the showing how the calculations could be done, he predicted where signatures in Saturn's rings would be. He also noted that the Cassini mission, then in the planning stages, would be able to make the observations needed to try this idea.

"Two decades later, in the last year of the Cassini mission, scientists analyzed mission data and found ring features in the Mark's predictions," said Jonathan Fortney, a professor of astronomy and Astrophysics at Santa Cruz, CA. Member of the Cassini team. "This current task is to achieve most of these observations."

Cassini's mission ended in September 2017 when, low on fuel, the spacecraft was deliberately plunged into Saturn's atmosphere by the mission team, which wanted to avoid crashing the craft on the planet's moons.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency (ESA) and the Italian Space Agency. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission of NASA's Mission Mission Directorate, Washington. JPL designed, developed and assembled the Cassini Orbitry. The radar instrument was built by JPL and the US Space Team team member. There. And some European countries.

More information about Cassini can be found here:

News Media Contact

Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, California.
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JoAnna Wendel
NASA Headquarters, Washington
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