Online Astronomy eText: The Planets / The Sky
The Rotation of Saturn

The Overall Rotation of the Planet
     Since Saturn does not have a solid surface, it is difficult to define a rotation period for the planet as a whole. Different portions of its visible "surface", which represent different circulation systems in its atmosphere, move around its axis at different rates, according to whether they have westward or eastward motions relative to the overall rotation of the planet. "System I", which refers to the Equatorial region, has a rotation rate of around 10 hours 14 minutes, while "System II", which refers to non-Equatorial regions, has a rotation rate of around 10 hours 39 minutes. There is also a "System III" rotation, which refers to the rate of rotation of the planet's radio emissions, which was once thought to refer to the rotation of the "body" of the planet, and at the time of the Voyager flybys, was around 10 hours 39 minutes. However, in the years since then, the System III rotation period has increased to 10 hours 45 minutes, indicating that it is not associated with the "real" rotation of the planet. Alterations in the position of the radio field, and in the plasma field surrounding the planet (possibly caused by geyser eruptions on Enceladus), are thought to be responsible for the change in the System III rotation rate; but whatever the cause of these changes, they cannot be due to a change in the rotation of the body of the planet. So the once-hoped-for fundamental nature of the System III rotation period has been disproved, and there is no currently conceivable way of estimating the "real" rotation of the planet as a whole. A recent compilation of results yields a rotation period of 10 hours 32 minutes 35 seconds; but this value is like the proverbial two point something children per American family -- it may be mathematically useful, but it cannot be representative of any real family, since no family can contain a fraction of a child. In the same way, the compiled rotation period may be useful for some calculations (e.g., the comparison of roation period and day length mentioned below), but it has no correspondence to any real part of Saturn.
     Regardless of these uncertainties, there is no doubt that Saturn has the second-fastest rotation rate of any planet, both in terms of its rotation period, and the speed of its rotation at the Equator, which is just under 10 kilometers per second, or about 35000 kilometers per hour (or just under 6 miles per second, or about 22000 miles per hour). Only Jupiter has a faster rotational velocity or rotation period.

Difference Between Rotation Period and Day Length
     Since the rotation period of Saturn is so uncertain, the difference between its rotation period and day length is, for all practical purposes, unimportant; but as discussed at Rotation Period and Day Length, given its rapid rotation and long orbital period, the difference between the two values is only about one second. So no matter where you are on Saturn, whatever the local rotation period is, the length of the day is one second longer.

The Rotational Tilt of Saturn
     The axis of Saturn's rotation is tilted relative to its orbit by just under 27 degrees. This means that insofar as Saturn has seasons, they would be similar to those on the Earth, being relatively minor at the Equator, relatively extreme at the Poles, and in-between at in-between latitudes. However, since Saturn's temperature is over 200 degrees below zero Fahrenheit, even its warmest summers are very cold by Earthly standards, and seasons as we know them do not exist.
     Despite the lack of obvious seasonal effects, the tilt of Saturn's axis does produce a very easily observable effect, because the ring system of the planet and the orbits of virtually all of the planet's moons are very closely aligned to the planet's Equatorial plane. Therefore, as discussed at The Rings of Saturn, when we see Saturn near one of its polar summers, we see the rings from above or below, as a broad, spectacular oval; whereas when we see Saturn near the start of its spring or fall (as we do in 2008 and 2009), the rings are barely visible, due to our nearly edge-on view.