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Singing Saturn electric


Listen to the sounds of Saturn here (Image: NASA/JPL/Space Science Institute; Sound: NASA/JPL/University of Iowa/mp3 file, 291kb)

Weird radio broadcasts from Saturn, caused by the interaction between the solar wind and the planet's magnetic field, have been captured by the electronic ears of the Cassini spacecraft.

The loudest and most bizarre sounds are coming from the ringed planet's aurora, or northern and southern lights.

Dr William Kurth, of the University of Iowa, and team, report on the sounds of Saturn in the current issue of Geophysical Research Letters.

"Strangely enough, they are very similar to what we hear at Jupiter and Earth," says Kurth.

The reason for the similarity is that all three planets, along with Neptune, Uranus, Mercury and even Jupiter's moon Ganymede, generate their own magnetic fields that interact with charged particles steaming out from the sun.

When those particles are channelled to the magnetic poles of planets, they can create strange lights and other electromagnetic radiation, including radio waves.

"What's happening is all of the electrons bundle up together and spontaneously emit the electrical field" that is detectable as radio waves, says team member, Dr Don Gurnett, a pioneer of planetary radio emissions, also of the University of Iowa.

It's a truly weird thing, he says, and researchers aren't yet precisely sure how planetary magnetic fields are made.

Radio waves don't get through Earth's atmosphere

Jupiter has been known to broadcast its own radio emission since the early days of radio astronomy, says Gurnett.

But that's because Jupiter broadcasts in a wide range of frequencies, he said. Saturn sings the planet electric in a narrower band that doesn't make it through Earth's atmosphere.

Earth's own auroral radio emissions weren't detected until the late 1970s, says Gurnett.

That's because our own ionosphere, at the top of our atmosphere, filters out that particular band of radio waves.

The first time scientists discovered Saturn's radio emissions was when the Voyager spacecrafts made the first tours of the sixth planet back in 1980 and 1981.

At that time they were only able to record limited frequencies, listening and stepping up bands every few minutes.

In contrast, Cassini's instruments can get eight radio "spectrums" per second, says Kurth.

That makes for a far better resolution of what the planet is singing.

Saturn, says Kurth, turns into a planet-sized radio station when the charged solar wind flows and sort of bows Saturn's magnetic field.

That creates an emitter with one billion watts of power, he says. That's about 100,000 times more powerful than a well-equipped human-made radio station on Earth.

Besides just being eerie, the sounds of Saturn likely contain clues to the inner workings of Saturn that create the magnetic field, says Kurth.

Saturn's radio emissions could provide some clues to alien worlds as well, he says.

Already, team member Dr Philippe Zarka of the Paris Observatory in Meudon, France, has begun looking for similar radio signals from "hot" Jupiter-like planets orbiting other stars, says Kurth.

If or when he succeeds, it could reveal an unprecedented amount of detailed information about the structure of planets not yet seen in visible wavelengths.

Tags: astronomy-space, computers-and-technology, information-technology, physics