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About Saturn & Its Moons

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Magnetosphere - Recent Discoveries - Periodic Signatures

"What we learned from those previous flybys is that Saturn's magnetic axis is exactly aligned with its rotation axis," says Marcia Burton, investigation scientist. "What this means is that -- from the vantage point on a spacecraft such as Cassini sitting at a fixed point outside the planet -- the magnetic field does not change as the planet rotates approximately every 10 hours."

This is of particular interest to scientists because no other planet in the Solar System is like this. For example, at Jupiter, like Earth, the magnetic axis is tilted around 10 degrees from the rotation axis. This leads to a bobbing of the magnetic axis and periodic signatures in the magnetic field with each rotation of the planet.

Data obtained by Cassini confirm that the magnetic field is basically symmetric about the planets rotation axis. However, scientists have now discovered a strong and steady signal in the magnetic field repeating with a period of 10 hours and 47 minutes, an unlikely signature for a symmetric magnetic field. This signature in the data has persisted since Cassini entered Saturn's magnetosphere on June 27, 2004.

Surprisingly, a similar periodicity is seen in other measurements that characterize the magnetosphere, including emissions of a certain type of radio waves known as SKR, energetic electrons, and energetic neutral atoms.

"We are puzzled by a periodic signature in the data, a signature that persists even in the outer portions of the magnetosphere," Burton explains. "Pinning down the mechanism behind this periodic modulation is a prime goal of Cassini scientists studying the magnetosphere."