Tracking the rotation speed of Saturn has been extremely difficult in the past because its gaseous surface is obscured by clouds, preventing easy visual measurements from satellites, and some areas even move at different speeds. A new measurement method could help finally determine the planet's rotation period.
The insight gained from this method could reveal clues about the internal structure of Saturn, as well as how it was formed, Tel Aviv University reported. The technique is based on measurements of Saturn's gravitational field and takes into account the fact that the planet's east-west axis is shorter than its north-south axis.
The findings show that Saturn's day is 10 hours, 32 minutes, and 44 seconds long. The researchers tested the method by also applying it to Jupiter, whose rotation period is already well known, and found the results checked out.
"In the last two decades, the standard rotation period of Saturn was accepted as that measured by Voyager 2 in the 1980s: 10 hours, 39 minutes, and 22 seconds," said Tel Aviv University researcher Ravit Helled. "But when the Cassini spacecraft arrived at Saturn 30 years later, the rotation period was measured as eight minutes longer. It was then understood that Saturn's rotation period could not be inferred from the fluctuations in radio radiation measurements linked to Saturn's magnetic field, and was in fact still unknown."
The revealing new method is based on a statistical optimization method that included a number of solutions such as a reproduction of Saturn's observed properties.
"The rotation period of a giant planet is a fundamental physical property, and its value affects many aspects of the physics of these planets, including their interior structure and atmospheric dynamics," Helled said. "We were determined to make as few assumptions as possible to get the rotational period. If you improve your measurement of Saturn's gravitational field, you narrow the error margin."
In the future, the researchers hope to apply the newly-developed technique to other gaseous planets such as Uranus and Neptune.
The findings were published in a recent edition of the journal Nature.
